Research Methods on Farm Use of Tractors 9780231889667

Table of contents :
EDITORS' FOREWORD
ACKNOWLEDGMENTS
CONTENTS
TABLES
CHARTS
INTRODUCTION
RESEARCH METHODS ON FARM USE OF TRACTORS
I. Types of Tractors
II. Size of Tractors
III. Grouping of Farms according to the Type of Power
IV. Methods of Computing the Cost of Operating Tractors
V. The Procedures Followed in Power Investigations
VI. The Basis for Comparisons of the Costs of Farm Power
VII. Adjustments of the Cost of Power
VIII. The Effect of Farm Size on the Cost of Power
IX. Selecting the Area
X. Summary
APPENDICES
I. Rated and Adjusted Horsepower of Tractors
II. The Recommended Method of Computing the Rate for Depreciation of Tractors, with Comparisons
III. Some Details of the Application of the Recommended Method of Computing the Charge to Depreciation
IV. Derivation of Depreciation Formulae
Bibliography
Index

Citation preview

RESEARCH METHODS ON FARM USE OF TRACTORS ft NUMBER

COLUMBIA

FIVE

UNIVERSITY

H I S T O R Y OF A M E R I C A N

S T U D I E S IN

THE

AGRICULTURE

RESEARCH

METHODS

ON F A R M U S E OF TRACTORS

BY

N. J A S N Y

NEW YORK : MORNINGSIDE

HEIGHTS

COLUMBIA U N I V E R S I T Y PRESS 1938

COPYRIGHT COLUMBIA

UNIVERSITY

1938 PRESS,

NEW

YORK

Foreign agents: OXFORD UNIVERSITY PRESS, Humphrey Miljord, Amen House, London, E.C. 4, England AND B. I. Building, Nicol Road, Bombay, India; KWANG H S U E H P U B L I S H I N G HOUSE, 140 Peking Road, Shanghai, China; MARUZEN COMPANY, LTD., 6 Nihonbashi, Tori-Nichome, Tokyo, Japan

Manufactured in the United States oj America

COLUMBIA HISTORY

UNIVERSITY

S T U D I E S IN

OF A M E R I C A N

THE

AGRICULTURE

ft EDITED

BY

HARRY J. CARMAN P R O F E S S O R OF H I S T O R Y

IN C O L U M B I A

UNIVERSITY

AND

REXFORD G. TUGWELL ft ADVISORY E V A R T S

B.

C.REF.NE,

BOARD

Chairman,

PROFESSOR

OF

HISTORY

IN

COLUMBIA

UNIVERSITY A V E R Y

O. C R A V E N ,

E V E R E T T

E.

P R O F E S S O R OF H I S T O R Y I N T H E U N I V E R S I T Y OF C H I C A G O

E D W A R D S ,

M A N A G I N G E D I T O R OF L E W I S

C. G R A Y ,

UNITED

STATES

Agricultural

DEPARTMENT

OF

AGRICULTURE;

History

E C O N O M I S T , D I V I S I O N OF L A N D E C O N O M I C S , U N I T E D S T A T E S

D E P A R T M E N T OF A G R I C U L T U R E H A R O L D

A.

1NNIS,

P R O F E S S O R OF P O L I T I C A L E C O N O M Y IN T H E

UNIVERSITY

OF TORONTO L O U I S

B.

SCHMIDT,

P R O F E S S O R OF H I S T O R Y

OF A G R I C U L T U R E AND M E C H A N I C A L W A L T E R

P.

W E B B ,

PROFESSOR

OF H I S T O R Y

ft

IN

T H E IOWA S T A T E

COLLEGE

ARTS IN T H E

UNIVERSITY

OF

TEXAS

EDITORS' FOREWORD IF THE American farmer of a hundred years ago could today travel up and down the broad countryside of the United States, he would be amazed at the transformation. He would discover not only that the nation's farming area has greatly increased in size but also that the whole process of American agriculture has been revolutionized. Of all the changes which he might note, none perhaps would impress him more than the extent to which agriculture has been almost completely mechanized. Instead of gangs of muscle-hardened, perspiring men, toiling long hours with hoes, forks, scythes, rakes, sickles, cradles, flails, and other primitive tools, he would find sulky and gang plows, mowing machines, hayrakes, tedders, loaders, stackers, grain drills and binders, corn planters and harvesters, threshing combines, milking machines, and mechanical cotton pickers. He would also ascertain that even in those areas devoted to the production of fruit and vegetables mechanical spraying apparatus is considered indispensable. The effect of these mechanical improvements upon the productivity of agricultural labor has been little short of remarkable. The modern combine, for example, can reap and thresh from 60 to 125 acres of grain a day. If the 1926 Kansas wheat crop had been harvested by the methods in vogue a hundred years ago, 775,000 harvest hands working 20 days would have been needed to cut, bind, and shock the crop. To put it differently, had Kansas been called upon to harvest its wheat crop of that year by hand methods, it would have required all the male population of the state between the ages of 15 and 60 years, and, in addition, all the women of the state between the ages of 20 and 37 years. In a word, without agricultural machinery the agricultural output of the nation since 1850 would have been impossible. The extent to which its use has lightened the burden of farm labor is perhaps incalculable. For many years nearly all of these machines depended in whole or in part upon the power of horses and mules. In a few localities steam engines were used for threshing purposes before the Civil War, and by 1879 no less than 80 percent of the grain

viii E D I T O R S ' FOREWORD in the outstanding grain-growing areas of that time was threshed by steam power. Great steam-propelled tractors were also in use in a few localities. It was not until the twentieth century, however, when the motor truck and the gas-driven tractor made their appearance, that the need for work animals began to diminish. In 1920 nearly 246,000 farms reported tractors. Ten years later the number had reached 851,000, and in 1936 the estimated number was placed at 1,205,000. These tractors were not all of the same design and consequently differed considerably in horse power and in usefulness. Several scientific studies have been made in recent years concerning the tractor as a labor- and power-saving device. In the pages which follow, Dr. Jasny, a noted tractor authority, has examined critically these several studies, pointing out wherein lie their merits and demerits. At the same time, he has set forth his own ideas for determining the usefulness of the farm tractor now in use in this country. H. T. C. R. G. T. COLUMBIA UNIVERSITY TN T H E C I T Y OF N E W YORK

March 8, 1938

ACKNOWLEDGMENTS for the writer to acknowledge his innumerable obligations to all the persons who in different ways assisted him in the preparation of this study. To Professor Harry J. Carman, Columbia University, who made possible the publication of the study by including it in his series, the writer is indebted the more since the scope of research covered by the series had to be extended to include this study. The writer is grateful to Dr. J. S. Davis, Director of the Food Research Institute, California, for encouragement in completing the study. The writer is also well aware of his obligations to Professor Carter Goodrich, Columbia University. The derivation of depreciation formulae presented in Appendix IV (pp. 258-59) is the work of H. J. Wadleigh of the State Department. The writer wishes to acknowledge the courtesies of Dr. C. L. Holmes, formerly in charge of the Division of Farm Management and Costs, Bureau of Agricultural Economics, United States Department of Agriculture, and M. R. Cooper, assistant chief of the same Division, in extending the facilities of the Division. To Dr. Eric Englund, Assistant Chief of the Bureau of Agricultural Economics, United States Department of Agriculture, the writer is indebted for permission to have the graphs prepared by the Graphic Section of the Bureau. Thanks also are due to R. S. Hainsworth, in charge of the Graphic Section of the Bureau of Agricultural Economics. A grant-in-aid from the Social Science Research Council enabled the writer to make an extended field trip which proved very useful by supplying much information, by clarifying many points, and by giving opportunity for extremely desirable contacts with persons on the spot. R. B. Gray, Chief of the Division of Mechanical Equipment of the Division of Agricultural Engineering, United States Department of Agriculture, and W. M. Hurst, Assistant Agricultural Engineer of the same Division, were consulted on mechanical problems of tractor construction and tractor work. M. R. Cooper, Senior Agricultural Economist; R. D. Jennings, Senior Agricultural Economist, both of the Division of Farm I T I S IMPOSSIBLE

X ACKNOWLEDGMENTS Management, Bureau of Agricultural Economics; and S. S. Speelman, Associate Animal Husbandman, Animal Husbandry Division, Bureau of Animal Industry, United States Department of Agriculture, were consulted on the cost of horse work. G. W. Collier, Associate Agricultural Economist; M. A. Crosby, Associate Agricultural Economist; R. S. Kifer, Senior Agricultural Economist; K. H. Myers, Associate Agricultural Economist; and Emil Rauchenstein, Senior Agricultural Economist, all of the Division of Farm Management and Costs; and J. L. Stewart, Agricultural Economist, Foreign Agricultural Service Division, Bureau of Agricultural Economics, United States Department of Agriculture, read the manuscript, or parts of it, and freely shared their experience with the writer. The Department of Agriculture of the Dominion of Canada and the Agricultural Experiment Stations of Illinois, Indiana, Missouri, and Montana kindly supplied the author with valuable data supplementing their publications on farm power. To the Department of Agricultural Engineering of the University of Nebraska the writer is indebted for criticism of the part of the manuscript devoted to the measurement of tractor power. The writer appreciates the valuable assistance of Mrs. A. V. Laslie, Division of Farm Management and Costs, in handling the statistical work, and of Miss G. W. Read, who helped to prepare the manuscript for the press. It was a pleasure to have been aided also by Miss L. Garton of the Foreign Agricultural Service Division. N.J. WASHINGTON,

D.C.

March 24, 1938

CONTENTS Vll

Editors' Foreword Acknowledgments Introduction

. xvii

I. Types of Tractors

3

II. Size of Tractors

14

III. Grouping of Farms according to the Type of Power

48

IV. Methods of Computing the Cost of Operating Tractors . . . . . . . .

57

V. The Procedures Followed in Power Investigations . 122 VI. The Basis for Comparisons of the Costs of Farm Power . . . . . . . . 149 VII. Adjustments of the Cost of Power

.

.

.180

VIII. The Effect of Farm Size on the Cost of Power .

. 199

IX. Selecting the Area

224

X. Summary

229 APPENDICES

I. Rated and Adjusted Horsepower of Tractors .

. 242

II. The Recommended Method of Computing the Rate for Depreciation of Tractors, with Comparisons . 254 III. Some Details of the Application of the Recommended Method of Computing the Charge to Depreciation . . . . . .256 IV. Derivation of Depreciation Formulae . Bibliography Index

.

. .

. .

. .

. .

. .

.258

. .

. .

.261 .

267

TABLES 1. Performances of a wheel-tractor and a crawler according to Montana experiments . 1 0 2. Acres covered per ten-hour day by three-plow and four-plow tractors in the Prairie Provinces of Canada . . 2 3 3. Proposed grouping of tractors by size . . . 4 4 4. Effect of the age of tractors on the charge to depreciation, determined by the inventory method . . . 7 0 5. Effect of the age of tractors on the cost of repairs . . 97 6. Items of costs of operating a wheel-tractor with 10-11 adjusted drawbar horsepower, of average age, in the Corn Belt in the second half of 1933 116 7. Cost of operating horses in the Corn Belt in the second half of 1933 118 8. Cost of power, labor, and machinery per crop acre for growing and harvesting crops in Linn County, Missouri, 1930, in percentage of corresponding expenditures on corn .143 9. Power requirements of various crops in hours per crop acre in Georgia, 1929 ISO 10. Normal power requirements of various crops in Oklahoma, 1931 151 11. Normal power requirements of various crops in Purchase Region, Kentucky 151 12. Power requirements of wheat in Montana . .152 13. Acres in cotton, in percent of total crop acreage, in Georgia 156 14. Labor used per crop acre for growing and harvesting crops in the Corn Belt, and its relation to the amount of power used for the same crops . . . . .183 15. Schematic pattern of a computation of the saving of labor resulting from utilizing tractors . . . . .189 16. Cost of machinery per crop acre for growing and harvesting crops in Linn County, Missouri, 1930, and its relation to the amount of power used for the same crops . . 192 17. Effect of tractors on acreage and on the number of horses displaced on wholly mechanized farms in the Prairie Provinces of Canada . . . . . . . . 206 18. Cost of all power on general-purpose tractor farms, Corn Belt, 1929 216

CHARTS 1. Manufacturers' ratings of drawbar horsepower expressed in percent of maximum drawbar horsepower . . . 3 2 2. Prices of tractors, 1926-36 59 3. Yearly depreciation charge of tractors of different age, determined by application of the inventory method . . 69 4. Yearly depreciation charge of tractors, expressed in percent of first cost, as computed by different methods . . . 7 6 5. Cost per hour of operating a wheel-tractor with 10-11 adjusted horsepower at different ages, as computed by application of the recommended method . . . .109 6. Fixed and variable costs of horse and tractor power, in percent of total cost . . . . . . . .119 7. Cost of horse and tractor power per hour and per horsehour equivalent, respectively, for different amounts of annual use of horses and tractors . . . . . 120 8. Differences in cost of horses, machinery, and labor per crop acre between horse and general-purpose tractor farms in Central Illinois, before and after adjusting these costs for variations in the amount of livestock . . .136 9. Differences in cost of horses, machinery, and labor per crop acre between ordinary tractor farms and general-purpose tractor farms in Central Illinois, before and after adjusting these costs for variations in the amount of livestock . .140 10. The effect of eliminating differences in the amounts of drawbar power used per crop acre, on the comparative cost of drawbar power on a horse and a tractor-and-horse farm in Central Indiana . . . . . . .154 11. Cost of power per crop acre for different kinds of work on horse and tractor-and-horse farms in the Com Belt, 1929 160 12. The effect on the comparative cost of drawbar power of eliminating the differences in the amounts of drawbar power used per crop acre, Com Belt, 1929 . . . .164 13. Cost of horse and tractor power per horse-hour equivalent on farms with different amounts of power work . .201 14. Variations in the cost of power per crop acre on farms of different sizes and with different types of power, Corn Belt, 1929 204 15. The effect of eliminating the differences in the size of farms on the cost of power per crop acre, on general-purpose tractor farms and on horse farms, Corn Belt, 1929 . .210

INTRODUCTION ONE OF THE prerequisites for efficient research work is a proper division of time and attention between factual and methodological studies. Too much attention devoted to methodology may result in there being so few fact-finding studies that even with application of the best methods the knowledge attained will be only meager. Similarly, even ample data will not provide reliable knowledge if there is concentration on factual studies at the expense of exact methods. Unfortunately, a disproportionate division of energy between factual and methodological studies is evident in former investigations of the utilization of tractors on farms. A student interested in this subject, in whatever country he may live, is forced to come to the United States for information. Probably more studies of the utilization of tractors on farms have been made in this country than in all the rest of the world. Many states have issued one or more publications dealing exclusively or in part with tractors, and the United States Department of Agriculture also has published several such studies. The factual material available in this country is almost too voluminous to be handled conveniently. Yet, so far as the present writer is aware, the only discussion devoted exclusively to methods to be used in these investigations is a brief article by Tolley in Research in Farm Management.1 The investigators, however, who are occupied with factual studies and are anxious to publish the results before they become obsolete, are not always able to devote the necessary time and attention to the problems of method. Under these conditions, it is only natural that some of the findings of previous studies should be unreliable because of the use of inadequate methods. Still more frequently, findings of independent studies cannot be compared because different methods have been followed by the authors. A comparison of the findings of studies made in regions where conditions are similar, however, is of immense significance in checking results, 1 "To Determine the Economy of Using Tractors in a Specified Type-ofFarming Area," pp. 204-10.

xviii

INTRODUCTION since it provides a basis for eliminating findings which may be only accidental—the results, for example, of investigating an insufficient number of farms. Comparisons of findings for regions where conditions are unlike are also of great importance, supplying, as they do, material for the investigation of the factors that determine the competitive position of tractors with relation to other sources of power. A few examples will show the results of using unstandardized and inadequate methods. According to different studies, the performances of three-plow tractors in plowing show a range of from seven to fourteen acres per ten-hour working day. Differences in the kind of soil or the depth of plowing could account only in small part for such immense variations. The explanation lies rather in the fact that tractors differing in power were classed as three-plow tractors in studies made in different states simultaneously, in the same states at different times, and even in the same states at the same time. Again, the cost of operating three-plow tractors of approximately the same size in two states situated not very far from each other was computed at $1.27 and $0.76 per hour respectively. T h e main reason for this great difference is that in one study $244.80 was set aside for the yearly depreciation, and in the other only $89.94, although there was no great variation in the annual utilization, which amounted to 51 days per year on the farms of the first state and to 40.2 days on those of the second state. Obviously, the answer to the question, Is it profitable to use tractors? may vary as the cost of operation under similar conditions ranges from $1.27 to $0.76 per hour. Yet the great variation in these figures is primarily the result of applying different methods of computing the cost of power, of which only one, if any, is correct. A third example: In a rather detailed study which used the cost of drawbar power per crop acre as a basis of comparison, this cost was found to be higher on farms using three-plow tractors than on horse farms. When a more appropriate method of comparison is used, the cost becomes higher on the horse farms. In another study, the cost of power on a tractor farm and the cost on a horse farm were equal, on the basis of crop acres. But it becomes less favorable for the tractor farm when an adequate basis is substituted for the crop acre.

INTRODUCTION

xix

I n the Supplementary Report of the Land Planning Committee to the National Resources Board, the following statement may be found: "A . . . comparison in the period of 1931 to 1932, during which time feed prices were at extremely low levels, showed that power developed by horses cost from 50 to 100 percent more than the power developed by tractors." The comparison referred to in this statement was made for the Corn Belt, in a publication of the Federal government. But the feed prices of the Corn Belt are almost the lowest in the country, and, moreover, feed prices over the whole country have greatly advanced from the exceptionally low level of 1931-32. T h e reader of the report is forced to wonder why under these conditions even a single horse is still being used on farms. The comparison of the cost of tractor and horse power was made without considering that the hourly performance of a rated drawbar horsepower of a tractor is substantially less than that of an average horse in the Corn Belt. Moreover, the cost of tractor work per hour is increased further by the fact that, on an average, tractors are operated less hours per year than horses. It is hardly necessary to advance further proof that a thorough check of the methods used in power studies is urgently needed. Even a simple comparison of the methods employed by various authors may help in the elimination of the more seriously defective techniques. In the comparison of various methods, moreover, new ideas are likely to suggest themselves. It may be hoped that a special treatment of methods will carry them to a degree of usefulness which is not now attainable in investigations which concentrate not on developing the best methods of collecting and working up data but on drawing factual conclusions with methods already developed or easy to develop. The present writer has devoted considerable time to this study. His awareness of substantial shortcomings in the result may perhaps be accepted as proof of the great difficulties involved in the subject, and of the need for studies exclusively devoted to problems of method. The writer does not expect that the greater part of his proposals will be accepted. H e will consider his task fulfilled if students of farm power are made aware of the significance of methodology, even though the methods proposed in this study may be improved or entirely superseded. Only if the present attitude of laissez faire toward methods

XX

INTRODUCTION

should continue, would he tend to consider this work a failure. The problem of whether the use of the tractor is profitable is sometimes approached too hastily. Penetration into the problem reveals not only that great difficulties are involved, but also that in cases where the margin of profit or loss resulting from the use of a tractor is narrow, it is frequently impossible to obtain a reliable answer. The shift to tractor power involves much more than the replacement of some horses by a tractor. It affects practically the whole farm business. Tractors and horses do not perform the same work. Tractors are used for belt work; horses are not. Conversely, horses are used for hauling; tractors of common types are not. Thus the shift to tractor power affects every use of power on the farm. Labor, moreover, is frequently affected by the introduction of tractors still more than is power. The labor released by the tractor may be utilized for increasing acreage or productive livestock, or both, for more thorough cultivation, for a shift to crop or livestock enterprises requiring more labor (and more power). Other items, such as the cost of machinery and yields, too, may be affected by the change in the source of power. The first studies, made shortly after the introduction of the tractor, attempted to ascertain the usefulness of tractors by analyzing the situation on farms before and after the purchase of the tractors. But this approach was frequently vitiated by the fact that farm methods are constantly changing. The introduction of the tractor accentuates this transformation, so that evaluation of the results of the purchase of a tractor can seldom be based on a computation of expenses before and after its purchase, but must usually be founded on the farmer's estimate of what the expenses would be if he did not possess the tractor. In this estimate the farmer usually overlooks the improvements which would normally have been made, without the use of the tractor, since the time of its purchase. The following quotation illustrates this point: A group of farmers who were using general purpose tractors and who had kept records during the entire year were asked at the end of the year to estimate the number of months of hired labor that they believed had been saved by the use of tractors. The estimates of 50

INTRODUCTION xxi of these men showed an average saving of six and one-half months of hired labor, yet the analysis of their accounts and of the accounts for horse and standard-tractor farms of the same area showed practically the same labor costs for the farms of all three types.2 I t is mainly for this reason that the other approach to the problem—the comparison of the situation on tractor farms at the time of the investigation with that on horse farms—has come to be the standard procedure. Since comparisons between the situations on farms using tractors before and after the purchase of the tractor are not likely to be used in the future, this method of approach is not considered in the present study. 8 Extensive complications, however, are also involved in comparisons of tractor and horse farms. Higher cost of tractor power as compared with the cost of horse power may be offset by other differences between farms with different types of power. This may occur the more easily because differences in type of power affect the whole farm organization. Comparisons cannot, therefore, be restricted to the cost of power on tractor and horse farms. In these circumstances, how can the effect of the difference in type of power be analyzed without reference to all the other differences between tractor and horse farms? In the excellent Illinois study quoted above, 4 an attempt is made to solve the problem by comparing tractor and horse farms which, on the average, are similar in such essential respects as location 5 and size, as well as in the value of feed used per crop acre. Additional data, such as the proportion devoted to different crops, yields per acre, return per $100 worth of feed used, and sources and amounts of income, are also included for the farms investigated, so that the differences in these items, so far as they are present, may be taken into account in evaluating the effect of the difference in the type of power. The Illinois study has the merit of having drawn the attention of investigators to the supreme importance, for reaching reliable conclusions about relative costs of sources of power, of keeping * J o h n s t o n and Wills. A Study oj the Cost of Horse and Tractor Power on Illinois Farms, pp. 2 9 6 - 0 7 . 3 This w a s w r i t t e n before the publication of Cornell's Fo'wer on West Virginia Farms, in which t h e m e t h o d described is applied (p. 2 8 ) . ' J o h n s t o n and W i l l s , op. cit., pp. 3 1 3 - 1 7 . " O n l y all-tillable f a r m s in east-central Illinois were used.

xxii

INTRODUCTION

all other factors equal. Yet the procedure followed in the study is rather awkward. It reminds one of the time when the problem of assigning a value to each commodity was solved by determining this value in terms of every other commodity. The matching of records after the manner of Johnston and Wills has no prospect of becoming general and plays a subsidiary role even in the Illinois study. If the question of the superiority of tractors or horses is to be answered in a more general way than that employed in the "matched records," the first problem is to find a proper basis for comparison of the costs of power. The crop acre is most commonly used for this purpose, conclusions being drawn from a comparison of the cost of power per crop acre on tractor and horse farms. Some investigators confine themselves to such a comparison; since they ignore the effect of the use of tractors on the cost of such important items as labor, they cannot disclose whether and, if at all, to what extent tractors are profitable. Others try to adjust the cost of power per acre for variations between tractor and horse farms in the cost of labor, machinery, and the like. Not infrequently an attempt is made to solve the whole problem directly, by comparing the total costs of power, labor, and machinery per crop acre, with or without some additional adjustments for further variations in farm organization (the quantity of livestock, for example) and for further effects of the use of the tractor (for example, on yields). Conclusions as to the advantages of tractors drawn from a comparison of the cost per crop acre of power, labor, machinery, and the like evidently are based on the assumption that variations in the amount of work done per crop acre are eliminated in averages for farms with different types of power. The only precaution against such variations which is nearly always found in power studies is the selection of more or less homogeneous areas. 6 Sometimes the effect of the size of the farm on the cost of power is also eliminated from the original data. A check of the resulting figures, however, shows that the most thorough use " W e say " f o u n d " and not "taken," because uniformity of area is usually aimed at as a safeguard not against variations in the amount of work done per crop acre, but. against variations in the prices of feed, fuel, and the like.

INTRODUCTION

xxiii

of such safeguards is insufficient. A n increase in the size of the sample not only fails to eliminate the variation between horse and tractor farms in the amount of work done per crop acre, but may accentuate it. Hence it is necessary to replace the crop acre as a basis for comparison by some other more exact basis or bases. This change is not only necessary; it is also entirely natural. What reason, indeed, is there for comparing the cost of power or labor on the basis of the crop acre? T h e natural procedure is to use some specific measure directly related to the items in question. For power, the natural measure and the natural basis for comparisons of cost is energy usefully spent per time unit, expressed, for example, in horse hours or in horsehour equivalents. For labor the natural measure is energy spent per time unit, expressed in man hours or in man days. Even use of machinery can be reduced to a time basis. Since power, labor, and use of machinery cannot be measured in the same units, they should be treated separately. Hence comparisons of the cost of power and labor or of the cost of power, labor, and machinery should not be used in studies on this subject except under specific conditions. In Chapter V are discussed in detail the procedures which power studies usually follow in ascertaining the results of operating tractors. Chapter V I is devoted to a detailed analysis of the basis to be used in comparing costs of farm power. T h e horsehour equivalent is recommended for this purpose, instead of the crop acre. In Chapter V I I , the discussion turns to methods of considering the effects of the tractor other than those concerning the cost of power. Having established the unit of measurement for comparisons of the cost of power, as well as methods of adjusting the results for the effects of the different sources of power, probably the most important step is to take account of the effect of the size of farm (or more exactly, of the amount of power work done per farm) on the amount and cost of power on farms of all types of power. Variations in the amount and cost of power on farms of different sizes are very large, usually considerably larger than variations in the cost of power on farms of similar size but with different types of power. T h e farms studied, moreover, usually

xxiv INTRODUCTION show great differences in size. In addition, the average size of the horse farms investigated usually is considerably less than that of the tractor farms. The danger is very great, therefore, that the difference in cost of power between farms with tractors and farms with horses may be submerged in variations in the cost of power on farms of different sizes. The effect of the size of farms on the cost of power is discussed in Chapter VIII. Findings supposed to apply to tractors and tractor farms in general are nearly valueless. Subdividing tractor farms into a greater number of groups, according to the type of tractor used, seems inevitable. The role that ordinary tractors can play on farms with a great proportion of row crops is fundamentally different from that which general-purpose tractors play. Under suitable conditions a general-purpose tractor may be profitable when an ordinary tractor would only involve a loss. To group rubber-tired tractors with tractors having steel wheels may be as inaccurate as to group ordinary tractors having steel wheels with similar general-purpose tractors. The classification of tractors, and of tractor farms by the types of tractors operated on them, is discussed in Chapter I. The power of the tractors used in agriculture varies from about 6 to nearly 60 adjusted drawbar horsepower. Even of the two tractor sizes most used, one exceeds the other in power by about SO percent. It is therefore essential not only to determine the size of tractors, but also to group them according to size. Thus the problem of measuring the size of tractors arises. Both measures of tractor power used for this purpose in power studies (the "plow" and the horsepower) are, however, indefinite and frequently variable, precluding the possibility of applying the simplest rules of statistical analysis to the data. The measure of tractor power and the class interval used in grouping tractors by size are discussed in Chapter II. The cost of tractor work and its value vary, depending on whether the tractor is used as the main source of power or only for auxiliary purposes. Hence it is necessary to make distinctions between farms not only by type and size, but also according to the proportion of power work assigned to the tractor (see Chapter I I I ) . All the care expended on choosing the proper basis for com-

XXV INTRODUCTION parison of the costs of power (and of labor and machinery), in eliminating the effect of the size of farms on the cost of power, and in getting the farms properly grouped by type of power may be wasted if inadequate methods of computing the cost of tractor or horse power are applied. The example given above (p. xii) shows that the application of different methods may bring about entirely opposite inferences as to the superiority of one or the other source of power. And yet, of all the phases of the study of farm power, that dealing with the methods of computing the cost of tractor power has unfortunately received least attention. A rather detailed treatment of the problem, therefore, seems necessary here (see Chapter IV). Since the usual procedure in selecting the area to be studied is open to no serious objections, only a few remarks concerning it seem necessary. These are included in Chapter IX. With regard to terminology, it is usual to designate as tractor farms those on which tractors are used, whether they are operated with tractors alone or with both tractors and horses. Logically, horse farms should then mean farms on which only horses are used, as well as those on which both horses and tractors are employed. The expression horse farm, however, is never used in this sense; only farms with horses but without tractors are designated as horse farms. In order to keep as close as possible to the common terminology, this study uses the expression horse farm in the usual manner. More exactly, horse farms may be defined as farms not using owned tractors for drawbar field work and not using hired tractors for more than 10 percent of the total drawbar field work. Farms not using owned horses for drawbar field work and not using hired horses for such work to the extent of more than 10 percent of the total drawbar field work are designated as wholly mechanized farms.1 Farms which are neither horse farms nor wholly mechanized farms in the sense of the above definitions are designated as tractor-and' The expression "horseless farm" employed for these farms b y Hopkins, et ai., in Cost of Producing Farm Crops in the Prairie Provinces, is hardly appropriate for general use (for the prairie states and many other regions it is correct), owing to the existence of small farms which o w n neither horses nor tractors. T h e distinction between owned and hired power in the definitions of type-of-power farms was first made by Sommerfeld in his paper on "Economic Aspects of the Horse Industry in Western Canada."

xxvi

INTRODUCTION

horse farms or horse-and-tractor farms." Finally, the expression tractor farm is employed in cases where it is merely desired to indicate that the farmer operates a tractor, but may or may not own horses. The expression farm with tractors is used alternatively to designate the same meaning. It is impossible to do without at least one of these rather indefinite expressions, for usually it cannot be ascertained that a group of farms designated in investigations as tractor farms does not include some that are entirely mechanized. ' The expression "horse-and-tractor farm" is employed for these farms by Smith and Jones, in Power, Labor and Machine Costs in Crop Production, Linn County, Missouri, 1930, and by some other investigators. In the South, the expression "combination farm" is used to designate farms with both sources of power. The choice between the two terms is a matter of taste. Tractor-andhorse farm, or vice versa, has been selected for its greater exactness. Whenever the proportion of drawbar work done with either source of power is known, it would be advisable to use the expression tractor-and-horse farm for farms on which the percentage of drawbar field work done by tractors is higher than SO percent of total drawbar field work, and vice versa. (See Sommerfeld, op. cit., p. 83.)

RESEARCH METHODS ON FARM USE OF TRACTORS

I T Y P E S

O F

T R A C T O R S

of tractor farms according to type of power used is one of many instances of the great variations that exist in the manner of dealing with power studies. Fain et al., in the Georgia study, give in Table 2 a distribution of the tractors studied according to size, but not type. In the other tabulations of the study, distinctions of size are also disregarded, all computations being made simply per tractor or tractor farm. On the other hand, Saville and Reuss in the study on Tractors and Trucks on Louisiana Rice Farms, 1929, presented some of their data separately for each make of tractor. In still other computations of the study, tractor farms were portioned out into five groups according to the number and size of their tractors, as follows: (1) one small tractor; 1 (2) one large tractor; (3) one large and one small; (4) two large; and (5) more than two tractors. A similar degree of precision was attained by Reynoldson et al. with respect to use of tractors in the Corn Belt. They included in their survey only tractor-and-horse farms with one tractor, classifying them as farms with (1) ordinary two-plow tractors, (2) ordinary three-plow tractors, and (3) generalpurpose tractors. To leave no doubt as to the size of the generalpurpose tractors, a footnote indicated that when the study was made all general-purpose tractors were of the two-plow size.2

T H E CLASSIFICATION

The technical precision of other investigations lies between these extremes. For example, Johnston and Wills, the authors of the Illinois study, investigated more than a thousand tractorand-horse farms, but classified them into only two groups: those with ordinary tractors and those with general-purpose tractors. 3 Both groups comprised varying proportions of farms 1

Tractors with about 10 drawbar horsepower were designated as small ones. Reynoldson et al., Utilization and Cost oj Pouer on Corn Belt Farms, p. 4. But a more recent study of the Federal Department of Agriculture (Reynoldson et al.. Utilization and Cost of Power on Mississippi and Arkansas Delta Plantations, p. 3) disregards the size of tractors. ' T h i s remark is valid only for the main part of the study, which is based on data from farm financial records. In the "Detailed Tractor Cost Study," another part of the Illinois investigation, ordinary two-plow, ordinary three-plow, and general-purpose two-plow tractors are distinguished. 1

4 TYPES OF TRACTORS with more than one tractor; 18.4 percent of the farms with general-purpose tractors kept also an ordinary tractor. Some students have segregated farms without horses; some have not. Similarly, a distribution of farms with tractors and horses according to the proportion of tractor work to the total work is made occasionally but not often. Many similar differences in method could be cited. The present chapter deals with the different types of tractors. The size of tractors is discussed in the next chapter, while the other factors pertinent to the grouping of farms by type of power are treated in Chapter III. Three types of tractors must, in the first place, be distinguished : 1. Tractors with steel wheels 2. Tracklaying tractors (crawlers) 3. Tractors with rubber-tired wheels Each of the above groups should be subdivided into: a) Ordinary tractors b) General-purpose tractors The types of tractors that have most frequently been dealt with in power studies are: Ordinary tractors with steel wheels, mostly referred to simply as ordinary or standard tractors. General-purpose tractors with steel wheels. (Ordinary) crawlers. General-purpose tractors of the tracklaying type have not attained a wide distribution and are not considered in this study. The rubber-tired tractor has been developed recently and is, therefore, discussed only briefly. Moreover, the treatment of this type as well as of general-purpose tractors with steel wheels and crawlers emphasizes their differences from ordinary tractors with steel wheels. This eliminates the necessity of discussing the latter type separately. GENERAL-PURPOSE TRACTORS WITH STEEL W H E E L S

General-purpose tractors of the wheel type are specially adapted for cultivating row crops. They have a higher ground clearance than ordinary tractors of the same type, and are

S T Y P E S OF T R A C T O R S designed to turn in a smaller radius, so as to reduce the damage to the standing crops. The reduction of the turning radius is usually attained by providing the general-purpose tractors with only three wheels. So far as construction is concerned, all these differences are of relatively secondary importance. Yet from an economic standpoint the general-purpose tractor with steel wheels and the comparable ordinary tractor represent two different types. 4 T h e possibility of using the general-purpose tractor for cultivating row crops, as well as for performing the work done by the ordinary tractor, considerably broadens the scope of its utilization. On farms with a large proportion of their total acreage in intertilled crops, an ordinary tractor generally can be used only as the subsidiary source of power, whereas the generalpurpose tractor can be, and often is, employed as the main source—sometimes, even, as the only source—of drawbar power. 5 The number of possible combinations of different sources of power and, consequently, the chance of finding a combination in which each source of power is utilized most efficiently are greatly increased through the introduction of the general-purpose tractor. Studies in which general-purpose tractors have been treated separately 6 usually show that farms with such tractors have done better, on the average, than farms with ordinary tractors— sometimes considerably better. For example, according to the Corn Belt study by Reynoldson et al., farms with ordinary twoplow tractors and an average of 184 acres in crops kept, on the average, 5.2 horses; while farms with general-purpose tractors and an average of 196 acres in crops needed only 4.4 horses and could probably have managed with fewer, although the tractors on these farms were probably of slightly smaller size. The lesser number of horses in the second case was made possible by the fact that ordinary tractors were used for an average of only 301 hours per year, while the general-purpose tractors averaged 471 hours. In 1929, the farms with ordinary two-plow tractors spent ' T h e characteristics of the general-purpose tractors with steel wheels are also present in similar tractors with rubber-tired wheels. "The great significance of this distinction is discussed at some length below (see pp. S0-S1). "This has been done only for regions where intertilled crops are important.

TYPES OF TRACTORS $3.13 per crop acre for drawbar power for growing and harvesting crops, whereas the farms with general-purpose tractors expended $2.91, although more work per crop acre was done on the latter farms than on ordinary two-plow tractor farms. Similar advantages of farms with general-purpose tractors are revealed by the comprehensive Illinois study of Johnston and Wills. The horse, machinery, and labor cost per acre in 1930, adjusted for variations in livestock on the farm, was, on the average, about 3 to 4 percent lower on farms with general-purpose tractors than on farms with ordinary tractors. 7 In the Corn Belt study and in some other studies, the more favorable showing of general-purpose tractors as compared with ordinary tractors results in part from the methods employed in computing the cost of operating tractors. 8 Moreover, during the depression the advantage of the general-purpose tractor was considerably reduced—in some instances probably wiped out— by the change in the ratio between the prices of feed on the one hand and the prices of tractors, tractor fuel, repairs, and the like, on the other. Of course the depression made this ratio considerably less favorable for all types of tractors, but tractors used as the main source of power were more adversely affected than tractors used as the subsidiary source of power. Especially is this true when we consider that the cost of operating a tractor should be lower for profitable utilization in the former capacity than in the latter. The difference in the cost of power used for growing and harvesting crops in the Corn Belt between the farms with ordinary two-plow tractors and the farms with general-purpose tractors amounted in 1929 to 22 cents per crop acre, or 7 percent of the total cost, in favor of general-purpose tractors; but in 1931-32 this difference was only 7 cents or 4 percent, according to computations of Reynoldson et at 6

In spite of the lesser advantage of the general-purpose tractor over the ordinary tractor under an unprofitable price relationship for agricultural products, an ordinary tractor of comparable size may be regarded as a poor investment on a farm with con' T h e assertion is valid only for the average of all farms in each type of power group. The figures by size groups reveal considerable irregularities. 1 See Chapter V, pp. 67-71 on depreciation, p. 96 on interest, and p. 100 on repairs. ' Utilization and Cost of Power on Corn Belt Farms, p. SO.

TYPES

OF

TRACTORS

7

siderable acreage in intertilled crops. The purchase of a tractor is rarely profitable unless accompanied by a diminution in the number of horses. But, if the tractor cannot be used for cultivation, such a diminution frequently brings about a shortage of available power at the time the crops have to be cultivated. There is indeed no reason for buying a tractor which cannot be used for cultivating, as a tractor adapted for cultivating and capable of doing all the work performed by ordinary tractors can be bought for practically the same money. T h e change effected by the introduction of the general-purpose tractor in the significance of the tractor for regions with a large proportion of intertilled crops was so great that the findings based on many earlier studies became obsolete or at least lost a part of their importance. An examination of the history of tractors, for example, reveals that the first wheel-tractors which made mechanical power really significant for agricultural drawbar work were tractors which now would be considered too small to be classed as two-plow tractors. Between the time when larger wheel-tractors were added to the two-plow tractors and the time when the general-purpose tractors were introduced there was a marked tendency on the part of many farmers to exchange their two-plow wheel-tractors for wheel-tractors of larger size. After the introduction of general-purpose tractors, which at the outset were available only in the two-plow size, many farmers came to rate the usefulness of the general-purpose tractor for cultivating higher than the greater adaptability of larger ordinary tractors to belt work. Thus, the decision of many farmers to adopt the general-purpose tractor might have caused a reversal of the previous trend in the size of tractors. All data pertaining to the relative merits of different types and sizes of tractors which were collected before the introduction of the general-purpose tractor consequently became more or less obsolete for all regions of the country where row crops are significant. 10 When general-purpose tractors of larger size were 10 It may be of interest to note that the upward trend still persists, so far as wheat regions are concerned. Out of 90 farmers in the grain-farming areas ill eastern Washington answering the question "If buying a new tractor, what size would you get?" 42 answered that they would buy a larger tractor than they then had, 38 that they would buy a tractor of the same size, and 10 that they would buy a smaller tractor (Landerholm, The Economic Relation of Tractors to Farm Organization in the Grain Farming Areas of Eastern Washington). The desire

8 TYPES OF TRACTORS put on the market, the situation again became different. Farmers had to weigh the higher adaptability to belt work of the three-plow tractors against the disadvantage of the unavoidable loss when larger tractors are doing light work: for example, cultivating or haying. Recently, general-purpose tractors still smaller than the first ones have been placed on the market. The demand for these new tractors is very keen. Thus the situation has become still more complicated. While some farms with two-plow general-purpose tractors are shifting to generalpurpose tractors of larger size, others find the so-called "baby tractor" satisfactory for their needs. Studies in which no distinction is made between generalpurpose tractors and other tractors result in conclusions pertinent to neither type. For example, in Table 9 of the Missouri study11 the data shown are intended to make possible a comparison of horse farms and horse-and-tractor farms. Even such refined computations as the number of adjusted crop acres" per farm, per man, and per horse are presented. Farms with obsolete two-plow four-wheel tractors, 13 which in the year of the investigation were used on the average only 258 hours per year, are, however, included in the group of tractor-and-horse farms along with a smaller number of farms equipped with generalpurpose tractors having an average age of two years and used for 436 hours of work. It is therefore impossible to tell what part of the findings should be credited to tractors in general, and what part explained by the obsolescence of the four-wheel tractors and their inadaptability for cultivating. Data showing that on horse-and-tractor farms in Georgia14 13 percent of the cultivating of cotton and 8 percent of the cultivating of corn was performed by tractors would also gain in value from a statement of the number of tractors adapted by their construction to this operation. In regions where intertilled crops are important, generalof certain farmers to have larger tractors is particularly significant, as the tractors in use in that region at the time of the study were on the whole rather large. u Smith and Jones, Power, Labor and Machine Costs in Crop Production, Linn County, Missouri, 1930, p. 17. 12 For adjusted crop acres, see pp. 168-69 below. "Discontinued models; average age 8.3 years. " Fain et al., Utilization and Cost oj Farm Power in Georgia, Tables 7 and 11.

TYPES

OF

TRACTORS

9

purpose tractors can under no circumstances be put into one group with other tractors. Since four-wheel tractors have lost their significance for these regions, the investigators of farm power in these regions should confine themselves to the study of general-purpose tractors. A start in this direction has already been made. 15 TRACKLAYING TRACTORS

When investigators distinguish at all among various types of tractors, they are usually satisfied with a segregation of generalpurpose tractors. All other tractors are considered "ordinary" or "standard" tractors. Whether these tractors are of the wheel or of the tracklaying type (i.e., crawlers) is usually not stated. This distinction, however, is important. Unlike general-purpose tractors, which differ little in construction from ordinary wheel-tractors, crawlers have a peculiarity of construction (replacement of wheels by the "clumsy" track) so important that we can correctly speak of crawlers as a type mechanically distinct from tractors of the wheel type. The adhesion of steel wheels to the soil is very small. In order to raise it to the necessary level, the steel wheels are equipped with lugs which consume a considerable amount of power.16 The track of the crawler, however, provides the necessary adhesion with an expenditure of a small amount of power only. As the result, the tractive efficiency defined as the ratio between the drawbar power and the power developed by the engine is much higher in crawlers than in wheel-tractors. Of two tractors, one of the steel-wheel type, the other of the tracklaying type, both equipped with engines of 40 maximum horsepower, the modern tracklaying tractor will possess a maximum drawbar capacity of perhaps 32 horsepower or more, while the maximum drawbar capacity of the tractor on steel wheels will seldom exceed 28 horsepower and frequently is less. For developing the " See, for example, the detailed t r a c t o r study, part of the Illinois study, b y Johnston and Wills, in which the average cost of operating tractors per year and per hour (Table 3 2 ) is the only computation made for three groups of t r a c tors, all other computations pertaining t o general-purpose tractors only. 10 The power required to o v e r c o m e the rolling resistance of a wheel-tractor weighing 5,620 pounds at a speed of 3 miles per hour increased from 2.45 horsepower when the tractor was equipped with drive wheels without lugs to 6.3 horsepower for the same tractor with drive wheels equipped with 4-inch spade lugs. Davidson et al., Tractive Efficiency of the Farm Tractor, p. 259.

10

TYPES OF TRACTORS

same drawbar power, crawlers therefore require smaller engines while they utilize less fuel and lubricants per drawbar horsepower. The much greater gripping power of the crawler, moreover, makes possible utilization of a greater portion of the maximum drawbar horsepower of crawlers than of tractors with steel wheels.17 In Table 1 the performances of a wheel-tractor classed TABLE 1

PERFORMANCES OF A WHEEL-TRACTOR AND A CRAWLER ACCORDING TO MONTANA E X P E R I M E N T S " Maximum drawbar H P.': wheel-tractor, 29.36; crawler, 53.49

Operation

Plowing One-way disking Tandem disking Combining with combine sixteen-foot Combining with combine twenty-foot Combining with two combines twenty-foot

Wheeltractor

Crawler

Wheeltractor

Crawler

Wheel-tractor used more ( + ) or less ( —) power than crawler (in percent)

1.03 0.44 0.32

0.43 0.25 0.15

30.24 12.92 9.40

23.00 13.37 8.02

+31.5 - 3.4 + 17.2

Hours of tractor per acre

Maximum drawbar H.P. hours per acre

0.34

9.98

+55.5=

0.25

7.34

+ 14.3''

0.12

6.42

" Source: for the wheel-tractor, Starch, Farm Organization as A fiected by Mechanization; for the crawler, Diesel Power and Field Operating Costs. b Corrected to standard temperature and standard barometric pressure. ' Wheel-tractor with one combine 16'; crawler with two combines 20'. d Wheel-tractor with one combine 20'; crawler with two combines 20'.

as a four-plow tractor and of a Caterpillar 50 are compared on the basis of data from the Montana Agricultural Experiment Station. The time per acre given in the table is the "total time" of Starch's study, Farm Organization as A fleeted by Mechanization, and the "total operating time" of the study, Diesel Power and Field Operating Costs. The maximum drawbar horsepower of the crawler is computed from the highest permissible draw" One of the reasons is that the tractive efficiency of the wheel-tractor is further reduced substantially on soil with a loose surface, while the tractive efficiency of crawlers is not materially influenced by variations of traction surfaces. Davidson et al., op. cit., p. 260.

11 TYPES OF TRACTORS bar rating as established in Nebraska. That of the wheel-tractor is set at the power developed in the maximum drawbar test made in Nebraska, as corrected to standard temperature and standard pressure (see Appendix I). According to the data, the accomplishment of the crawler in plowing, the most important farm operation, was higher by about 30 percent per maximum drawbar horsepower than that of the wheel-tractor. The crawler was found still more efficient in harvesting with a combine, as compared with an average of the two figures for the wheel-tractor. It is probably safe to assume that in drawbar work crawlers do some 20 percent more work per drawbar horsepower than tractors with steel wheels. The strong adhesion of the crawlers to the soil makes them particularly adapted to hilly, light, and soft land. Sometimes, when the soil is too wet for the wheel-tractor, horses can be used, but the crawler can be operated on soil that is too soft even for horses. This difference is particularly important in the spring. Moreover, since the pressure exerted by crawlers on the soil is many times smaller than that exerted by wheel-tractors, the work of the crawlers cannot be harmful to the texture of the soil. Apart from their more valuable service, crawlers last considerably longer (see p. 93). The first cost and the cost of repairs, however, are sensibly higher.18 The superiority of crawlers on rolling surfaces and on very moist and light soil may be accepted as definitely proved. As regards more normal conditions of topography and soil, it is a widespread opinion that the advantages of the tracklaying tractors are not so great as to compensate for the additional expense. To what extent this is in accord with facts remains, however, to be ascertained. So far as the present writer is aware, no studies yet published have devoted special attention to a comparison of the work of both types of tractors. 19 M Because of considerable differences in cost of operating crawlers and steelwheel tractors (of which the chief is the higher price of crawlers and their smaller consumption of fuel) the proportion of fixed charges to the total operating cost is greater for crawlers than for steel-wheel tractors. " Such an investigation would have to consider all possible conditions and not be restricted to an average situation. The higher proportion of fixed charges to the total cost of operating crawlers makes it possible that a crawler which is more expensive to operate than an ordinary tractor at a total annual use of, say, 300 hours, may be cheaper in operation if the annual use is twice or thrice this figure.

12

TYPES

OF

TRACTORS

In the last decade, moreover, the price of crawlers equipped with carburetor engines has been reduced materially more than that of wheel-tractors (see Chart 2, p. 59). At the same time, the competitive position of crawlers was enhanced by equipping them with Diesel engines. Consequently the use of crawlers is spreading over into the level portions of the wheat belts. They find some place—mainly for custom work—even in regions with a large proportion of the acreage in row crops. The great differences in construction, adaptability to various conditions, and the composition of operating costs make it impracticable to combine crawlers with wheel-tractors jn one group.20 Where, as in the wheat regions of the Pacific states, crawlers predominate, it is preferable to exclude wheel-tractors altogether to having them in one group with crawlers. Likewise, it seems reasonable to exclude crawlers in regions with a high proportion of acreage in intertilled crops, and to make special investigations of these tractors in certain selected areas. There are only a few regions where a general investigation of farm power can not avoid dealing both with crawlers and wheeltractors. Fortunately these regions use only few general-purpose tractors. RUBBER-TIRED TRACTORS

Tractors equipped with low-pressure rubber tires can be used for transportation on highways as well as in the field. This fact alone may sometimes be sufficient reason for regarding them as a separate type. There are, moreover, important peculiarities in the drawbar field work performed by the rubber-tired tractors. The experiments conducted by the Agricultural Engineering Department of the University of Nebraska and many other experiments21 show that rubber-tired tractors at higher speeds " So long as the grouping of tractors according to the number of plows they can draw is preserved, the separation of tracklaying tractors from wheel-tractors may also be necessary because tracklaying tractors move on the average more slowly than tractors with steel wheels and draw more plows per adjusted drawbar horsepower. The performances of tracklaying tractors, as compared with those of wheel-tractors, may therefore be slightly less than is indicated by the number of plows the tractors are able to draw. " Smith and Hurlbut, A Comparative Study of Pneumatic Tires and Steel Wheels on Farm Tractors; Davidson et at., Tractive Efficiency of the Farm Tractor; McCucn and Silber, Rubber-tired Equipment for Farm Machinery; Zink et al., Comparative Field Tests of Rubber Tractor Tires and Steel Wheels.

TYPES

OF

TRACTORS

13

develop considerably more drawbar power than similar tractors with steel wheels, except on wet ground. Although rubber-tired tractors are no more efficient at low speed than tractors with steel wheels and sometimes even less efficient, they may be expected on the average to cover appreciably more acres in the same time. There are, moreover, some other advantages, such as a saving on fuel, greater comfort for the driver, and increased durability. If the rubber-tired tractor is properly handled, its advantages should sensibly offset the additional outlay for depreciation and interest. 22 Tractors now used with rubber tires were for the most part originally built for steel wheels. What rubber tires really mean for tractors will be clear only when tractors especially adapted for use with rubber tires and implements suitable to them have been developed and perfected. Increasing the number of types of tractors distinguished in power studies is very undesirable. The unavoidable increase in the number of farms which have to be included in the study may frequently render the study altogether impossible. Yet a study which intends to show which type of power is more profitable has to segregate rubber-tired tractors from other types. Such data, for example, as on time used for different operations apparently would be meaningless if they would represent averages for tractors with steel wheels and rubber tires. The data on the cost of power per hour also would be affected by putting together both types of tractors. Since the investment is materially increased by rubber tires, the rubber-tired tractor may prove profitable under some specific conditions (large annual utilization of the tractor, extensive use of the tractor for custom work or haulage), while data in which the results for steel wheels and rubber tires are averaged would yield only indifferent results. B A tractor with 12-14 adjusted drawbar horsepower, i.e., a modern twoplow tractor, equipped with rubber tires, costs approximately $200 more than the same tractor with steel wheels. Rubber tires are supposed to last about. 5 years.

II SIZE OF TRACTORS I N F O R M A T I O N ON T H E S I Z E OF TRACTORS

a table before us, we look first at the captions and stubs and then at the figures beneath and beside them. The captions and stubs are supposed to refer to something known; the figures under or beside them indicate certain qualifying facts. If, for example, the power of a team of four horses is known, the information that such a team is cutting eighteen acres of grain per day may convey some idea about the power necessary for cutting grain. If, however, nothing is known about the power of the team, the only procedure is to reverse the process, trying to get some idea of the power of this particular team from the fact that it cuts eighteen acres per day. Evidence is available that on the state farms of Soviet Russia the plowing of threequarters of an acre is considered the normal day's performance per horse.1 Since a comparable figure in similar regions of this country is about an acre per horse and per day, the assumption seems to be justified that the power of Russian horses is only three-fourths that of American horses in similar areas. In the case of tractors, if the data presented show only the performance of the tractor, but do not specify its size, the reverse procedure indicated above is the only means of arriving at some useful information. I F WE HAVE

The situation described is not hypothetical. In earlier studies, it was usually the rule to speak simply of tractors without any specifications, and the same procedure has been followed in certain comparatively recent studies, such as that by Lloyd and Hobson on the Relation of Farm Power and Farm Organization in Central Indiana. Even more recently, one of the most elaborate investigations of farm power, the Illinois study by Johnston and Wills, combined into one group, disregarding size, all ordinary tractors. 2 1

See Kisourin and Losa, Planning the Organization of a Section on State Farms, p. 192. ' No type, size, or age of the investigated tractors is distinguished in Cornell's recent study, Power on West Virginia Farms.

IS SIZE OF T R A C T O R S Moreover, even when information on the size of the tractors is presented, this frequently does not prevail in all tabulations. Gilbert, for example, in his very interesting study on tractors operated on New York farms, in several computations combined his very useful data on 171 two-plow tractors with figures on only ten three-plow tractors. In Table 14 of that study, data of exceptional interest are presented on the consumption of fuel and lubrication and on the cost of repairs, and so forth, classified by age of tractor. These data could be used to advantage if one were sure that the three-plow tractors were evenly distributed over the nine years covered by the table. It is impossible, however, that ten tractors be evenly distributed among nine groups. It is unfortunate that Gilbert did not part with his three-plow tractors, at least in some of his computations. The value of the computations regarding hours of tractor work expended in various operations per acre of various crops, presented in Tables 7-11 and 18-20 of the Georgia study by Fain et al., would also be enhanced if the size of the tractors were known. The variations in the power of horses in the same regions, and probably also in the whole country, are usually much smaller than the difference in power between the nearest tractor sizes, for example, between two-plow and three-plow tractors, or between tractors with 10 and IS drawbar horsepower. The largest tractors employed in agriculture are nearly ten times as powerful as those of the smallest size, while in the case of horses the usual margin rarely exceeds IS to 20 percent. In spite of the comparatively small variations in the power of work stock, information regarding the power of work stock on which data are presented is of great value to the investigator, and its absence is recognized as a serious deficiency. It is particularly inconsistent to omit information regarding the size of tractors in a study containing detailed information on the weight and age of work stock. 3 As time goes on, specifications as to the size of tractors in power studies are becoming increasingly exact. Moreover, it has ' F o r example, in the study Farm Power in the Yazoo-Mississippi Delta, by Long, compare Tables 12 and 14, devoted to the mule work and containing the average weight of mules in each t y p e - o f - p o w e r group, with Tables 2-5, devoted to tractors and without specifications as to size. The greatest variation in the average weight of mules happened to be only 14.3 percent between farms with mules only and farms with mules and trucks.

16 SIZE OF TRACTORS been recognized that data covering tractors of widely differing sizes are of no great value, even though the average size may be known. The grouping of tractors by size may now be considered an established practice. An equivalent procedure is to exclude from tabulations all tractors not falling within certain size limits. Thus in the Corn Belt study by Reynoldson et al., all investigated tractors were grouped into two-plow ordinary, three-plow ordinary, and two-plow general-purpose tractors. The precision attained even in this and similar studies is necessarily limited, however, by the inadequacy of the measures of power used by the investigators. T H E MEASURES OF THE POWER OF TRACTORS

In determining the power of tractors, power studies employ either one of two measures: (1) the "plow," that is the amount of power which actually draws a plow, or which is supposed to be necessary for drawing a plow; or (2) the horsepower (H.P.). The plow is the measure in common use, the horsepower being employed only occasionally. In the manner in which they are used, neither of these measures is adequate. The grouping by size being postulated as indispensable, tabulations should conform to the statistical rules applying to the handling of the class interval, the avoidance of overlapping, and so forth. Obviously, such compliance is impossible unless the measure—or, more precisely, the unit of measurement—is constant and exact. If it possesses these qualities, it may readily be split into fractions, thus achieving the necessary degree of exactness in computations for which the whole unit would be too large. Moreover, the unit of measurement should possess these characteristics of constancy and exactness, even though the investigator contemplates no grouping of the tractors by size and contents himself with computing the average size of all the tractors included in the study. All widely used measures answer these requirements. The acre, for example, which is used extensively, perhaps even too extensively, in farm studies, is both constant and exact, so far as measuring land areas is concerned. Neither the plow nor the horsepower, as used in power studies in connection with tractors, however, is constant or exact, and data based on these meas-

SIZE

OF

17

T R A C T O R S

tares do not lend themselves even to elementary analysis.

statistical

T H E P L O W AS T H E M E A S U R E OF T R A C T O R P O W E R

T h e use of the plow as the measure of the power of tractors i s of historical origin.* Formerly, mechanical drawbar power f o r field operation was applied exclusively to plowing. T h e use of the steam engine in the field for any other purpose than plowing has been exceptional. T h e first engines with internal combustion used for field work likewise appeared in a form adapted only to plowing. Even after the introduction of the tractor in its present form, tractors in some regions were for many y e a r s used exclusively for plowing. T h e plow as the measure of tractor power has outlived this early stage in the development of f a r m power, and its use persists at a time when the tractor has long been employed for all kinds of drawbar work in the field, as well as for belt work. T h e practice of employing the tool used for some specific kind of work as the measure of power is exceptional. When horses are the source of power, one does not use as a measure the fraction of a plow a horse can pull. Rather, the weight of horses is ordinarily used to indicate their power. It is equally anomalous to determine the power of a machine by its performance in some particular operation, instead of by some direct measure. Plows, combines, binders, threshers, and so on are rated not by the varying amounts of work these machines perform under different conditions, i.e., upon the basis of extraneous circumstances, but upon the basis of some definite properties inherent in them — t h e number and size of bottoms in plows, the width of the cutting device in combines and binders, and the like. Some experts maintain that the plow is a proper measure of tractor power because power thus measured reflects the effect of variations in the cohesion of the soil. It will be shown later that this fact constitutes a reason for discarding rather than for retaining the plow as a measure. Moreover, the factor of soil cohesion rarely enters into consideration in connection with the use of the plow as the measure of power. T h e real reasons for ' Specifically, bottoms of plows and not plows are thought of. It is, however, customary to speak of a plow, instead of the bottom of a plow, in this connection.

18

SIZE OF

TRACTORS

its use are convenience, the difficulties encountered in using the horsepower as a measure, and perhaps simply habit. It must be conceded that for practical purposes the plow as a measure of power has certain advantages. Tractors are bought primarily for field work, and plowing ordinarily is the most important single phase of field work. While a farmer may not know how many horsepower a tractor with a certain speed must have in order to draw a two-bottom plow on his farm, the information that a certain tractor will pull a stated number of plows may enable him to estimate the performance of this tractor in other operations. The use of the plow as the measure of tractor power, however, frequently results in misunderstanding and dissatisfaction, even when employed in this practical way. When used in research work, it is still less satisfactory. The reasons for the inadequacy of the plow in research work for measuring the power of tractors are its great variability and its inaccuracy. Changes in the amount of the power of tractors do not always result in corresponding changes in the number of plows tractors can pull. Moreover, the number of plows a tractor can draw is greatly affected by several factors entirely independent of tractor power. Thus, on the one hand, the plow does not reflect correctly certain factors which affect the amount of tractor power; and, on the other hand, it reflects several factors which do not affect the amount of power. Let us consider these two groups of factors somewhat in detail, beginning with an analysis of the power of the tractor as it affects the number of plows which the tractor can draw. Power is force times speed. One horsepower, for example, raises 550 pounds one foot per second. Changes in power thus may be the result of changes of force, or of speed, or of both. If a change in the power of a tractor is solely the consequence of a change in speed, the force5 remaining the same, the number of plows that can be pulled may not be altered. In this case the number of plows will fail entirely to indicate the change in the power of the tractor. During their comparatively short period of existence, tractors have shown great improvements in speed, a sharp increase taking place just after 1920. In subsequent years tractor speeds ' So far as drawbar power is concerned, the force of tractors is called drawbar pull.

SIZE

OF

19

TRACTORS

continued to increase, and probably they are not yet stabilized, even for tractors of the well-established types. These increases in speed are clearly reflected in the performances of tractors per plow. In the study of the Illinois Agricultural Experiment Station, published in 1921, 6 a day's performance in plowing with a three-plow tractor with steel wheels is given as seven acres. In 1929 it was about 11 acres, according to the data of the Corn Belt study; 7 and recent investigations give still higher figures for the steel-wheel tractors described as three-plow tractors. It can be assumed that the recent models provide about 75 percent more power per plow than was the case in 1919. Even tractors of similar type, constructed at the same time but by different manufacturers, show variations in speed which cannot always be ignored. And, finally, all tractors have at least three speeds. These numerous variations in speed result in an endless variability in the amount of power provided by tractors of the same size, as measured in terms of plows. Chief among the extraneous factors affecting the number of plows which a given tractor can pull are: ( 1 ) the size of the plows; ( 2 ) the cohesion of the soil; ( 3 ) the depth of plowing; and ( 4 ) the topography. The size of the plows has not been important as a disturbing factor, most farmers using fourteen-inch plows. But the recently introduced baby tractors now in great favor with farmers are supposed to draw either one plow larger or two plows smaller than the standard fourteen-inch. The number of plows with bottoms other than fourteen-inch is likely to increase materially. The cohesion of the soil varies greatly. According to J . B . Davidson,8 the resistance of the soil in plowing is equivalent to: Pounds per Square Inch

Type of Soil Sandy soil Sand loam Silt loam Clay loam Heavy clay Gumbo or adobe

'Handschin et al., The Horse and the Tractor, p. 214. ' Reynoldson el al., op. cit., p. 19.

' Agricultural Machinery,

p. 124.

3 3-6 5-7 6-8

7-10 15-20

20

S I Z E OF T R A C T O R S

Thus, even disregarding extreme cases, the plowing of one kind of soil may require one and a half and even twice as much power as the plowing of another type. The depth of plowing varies with crops, soil, climate, and method of cultivation. Intensive agriculture, for example, calls for considerably deeper plowing than is satisfactory for extensive agriculture. It is noteworthy that the cohesion of the soil and the depth of plowing seldom offset each other—in fact, their effect frequently is cumulative, heavy soil requiring deeper plowing than light soil. Unlike horses, tractors possess only a very limited capacity for being overloaded. According to Murdock, 9 some wheel-type tractors are unable to draw any load in high gear when the grade is more than 22.3 percent. The largest crawlers, which on level ground can draw as much as twelve plows, usually draw only eight plows on very hilly land. Tractors operated on hilly land therefore need considerably more power per plow than tractors worked on level surfaces. It thus becomes evident that, while entirely independent of the power of the tractors, such factors as size of plows, cohesion of the soil, depth of plowing, and topography may all have a considerable effect upon the number of plows a tractor can draw. Two tractors which draw different numbers of plows, but show similar performances in all other operations (and perhaps even in plowing), are similarly powered tractors. Tractors pulling an equal number of plows, but having different performances in all other operations (and perhaps also in plowing), are tractors with different amounts of power. T h e failure of the plow to reflect variations in speed, while responding to other factors having nothing to do with power, results in large variations in the power available per plow, even among tractors constructed during the same period. An additional disturbing factor is that some farmers fail to use an adequate number of plows with their tractors. T H E ACTUAL NUMBER OF PLOWS AS T H E MEASURE OF T H E POWER OF TRACTORS

T h e differences between tractors with regard to available power in relation to the number of plows which they can draw 'Mechanical

Tests on Tractor Farming Equipment,

p. 125.

21 SIZE OF TRACTORS under different conditions, or numbers of plows actually used with them, lead to unfortunate consequences when the number of plows actually used is made the measure of tractor power. If a number of tractors are classed according to the amount of their power, it may be expected that their performances, the acreage in crops on the farms using them, and the size of farm business will be more or less in proportion. If tractors similar in power are placed in different groups, however, or tractors with differing power in the same groups, such proportionality cannot be expected. Comparisons of findings based on the plow for tractors constructed before and after the early twenties, for instance, are invalid and mischievous, owing to the great increases in speed which occurred during those years. It is hardly necessary to stress the fact that if one of two tractors plows an area 80 percent greater than does the other, those two tractors are quite different machines and must be treated accordingly.10 Differences in speed may affect data based on the plow, even if the interval in the construction of the tractors is brief. If the results of comparisons, for example, show an increase in performances of tractors of the same plow-group, as they often do, it is uncertain whether this increase is attributable to an increase in the power available per plow, or to the more efficient use of tractors and to improvements in tractor implements. Similarly, if a comparison of the results of studies based on the plow as a measure reveals no decrease in fuel consumption per tractor, it is difficult to determine whether no improvements in fuel utilization have been made, or whether the improvements made have been offset by an increase in power per plow11 or by the fuller utilization of the power of the tractors. Since the work performed by the tractors, and not the number of plows they can draw, is significant, and since the performances per plow of rubber-tired tractors in plowing and in all other " T h o s e w h o have tried to study the history of the use of tractors on farms in an entire country, and even more in the whole world, know only too well what an obstacle is met with in the form of these two, three, and more plow tractors. T h e few publications which contain a list of investigated tractors are therefore of almost immeasurable value, although even the power of tractors known by name and year of manufacture can be ascertained with ease only for those tractors placed on the market in recent years (see pp. 31-36). 11 The changes in fuel consumption, if any, can sometimes be determined from the expenditure of fuel per acre. This is an example of the indirect approach which investigators are compelled to use.

22 SIZE OF TRACTORS operations are greater than those of tractors with steel wheels and crawlers, findings for different types of tractors, made on the basis of the plow as the measure of tractor power, are not comparable. Apart from plowing, only the disking of stubble land is affected to a sensible extent by the nature of the soil. In all other operations a tractor will cover about the same number of acres on all types of soil. With similar tractors included in different size groups, accomplishments proportionate to the number of plows used cannot be expected even in plowing, since the same tractors usually will average a higher speed when pulling a smaller number of plows. Thus comparisons of findings cannot be made, even for the same types of tractors, if the plow is used as the measure of power. Comparisons of the findings of different studies, however, are the most convenient and frequently the only available means of checking the results of individual studies, through elimination of inaccuracies caused by insufficiency of the data or other factors. These comparisons are a means also of revealing regional variations and, with the help of this information, of getting a more general idea of the place of the tractor in farm business. The Department of Agriculture of Canada has kindly made available to the writer the data concerning tractors included in the study, Cost of Producing Farm Crops in the Prairie Provinces, by Hopkins et al., in which tractors were grouped according to the number of plows used with them on the investigated farms.12 The study, very illuminating in many respects, shows that the apprehensions expressed with respect to the results obtained from the distribution of tractors on the basis of plows are entirely borne out by facts. Out of the 247 tractors constituting the three-plow size group, only 30 tractors were models not included also in the four-plow size group. In the four-plow tractor group, out of a total of 119 tractors only 63 were models not found in the three-plow size group as well.1® " T h e same procedure was followed in another study made in the Prairie Provinces of Canada. See Grest, "Cost of Tractor Operation on Prairie Farms in Western Canada." " I n making this computation, I. H. C. rated 15/30 and rated 22/36 were regarded as similar models. If these models are considered different tractors, 28 tractors included in the group of four-plow tractors were models found also in the three-plow group.

SIZE OF TRACTORS

23

Table 2, which offers a comparison of the performances of the tractors included in the Canadian study in the three-plow and four-plow groups, shows that in no operation, except in seeding and rod weeding, were the performances of four-plow tractors higher, by as much as one-third, than the performances of the three-plow tractors." Performances were not proportionTABLE 2

ACRES COVERED PER TEN-HOUR DAY BY THREE-PLOW AND FOURPLOW TRACTORS I N T H E PRAIRIE PROVINCES OF CANADA«

Operation

Plowing stubble Plowing sod One-way disking Disking-single Disking-tandem Cultivating Rod weeding Harrowing Seeding Binding

Tractor three-plow

Tractor four-plow

Four-plow tractor did more than three-plow tractor (percent)

12.6 7.6 26.6 62.1 34.4 35.0 47.5 98.7 42.0 30.3

15.7 8.9 32.2 72.9 35.7 37.5 64.4 123.0 55.2 31.6

24.6 17.1 21.1 17.4 3.8 7.1 35.6 24.6 31.4 4.3

° Source: Hopkins et al., Cosl of Producing Farm Crops in the Prairie Provinces

ate to the number of plows even in plowing. The tractors designated as four-plow tractors plowed only 17.1 percent more sod land than did tractors of the three-plow group.15 In another study conducted in 1927, the maximum drawbar horsepower of two-plow tractors at the rated speed, as established by Nebraska tests, showed a range of from 7.26 to 17.40 " Their performances would be expected to be about one-third higher than those of three-plow tractors, if the power of the tractors were proportionate to the number of plows they draw or are supposed to draw. Actually the ratio between the average power of the so-called four-plow and three-plow tractors on the market changes with every model removed, added, or replaced. So does the ratio between the average power of the size groups of tractors differ from study to study. See Table 3, pp. 44-45, and pp. 46-47. 15 The failure on the part of farmers to use with some of the four-plow tractors correspondingly sized implements cannot account in full for the relatively small performances of these tractors, particularly since the same failure, although to a smaller extent, probably occurred also on the farms using the three-plow tractors.

24

S I Z E OF

TRACTORS

horsepower, while that of the three-plow tractors was from 13.67 to 21.52. So large an overlapping of groups is not frequently found in other than power studies. The number of plows operated with the tractors on different farms is the only measure of tractor power reflecting variations in cohesion of the soil and similar local characteristics. Since it is not possible to secure reliable data by using the actual plow as the measure of tractor power, no alternative remains but to abandon the idea of taking into consideration the variations in cohesion and other properties of the soil. T H E ABSTRACT PLOW

Variations occurring on farms in the amount of power of tractors per plow are so great that the use of so variable and indefinite a measure as the "actual" plow is usually found inadequate, even in cases where no particular stress is laid on absolute exactness as, for example, in the trade. The ordinary practice, therefore, is to disregard to some extent variations resulting from differences in the texture of the soil, in the depth of plowing, and the like, even when using the plow as a measure of tractor power. Some more or less indefinite assumption is made as to the power which two-plow, three-plow, and other similarly designated tractors should possess. For example, some years ago it was rather generally accepted that about five drawbar horsepower were required per plow. It will be shown later, however, that for a long time the horsepower used as the measure of the power of tractors was as variable and as indefinite as the plow itself. The extreme vagueness of conceptions as to the power of twoplow, three-plow, and similarly designated tractors is clearly reflected in the manufacturers' recommendations of the number of plows their tractors can pull. For several models, no recommendations are made as to the number of plows, the manufacturers preferring to abstain from responsibility not only for factors inherent in their tractors but for factors extraneous to them. For many tractors no definite number of plows is recommended. For instance, two to three plows are suggested, the range between the upper and lower number frequently being even greater. One of the reasons for stating the number of plows in two figures probably is that the power of their tractors is as-

25 SIZE OF TRACTORS sumed by the manufacturers to be larger than in the general opinion would be necessary for drawing the lower number of plows, and less than would be considered necessary for the higher number of plows. To some extent also the two-figure recommendations are intended to meet differences in texture and other properties of the soil, in the depth of plowing, and in other factors. However, whether expressed in one figure only or in a range, manufacturers' recommendations of the number of plows to be used with their tractors show material variations in the amount of power available per plow. Wheel tractors, tested in Nebraska 1930-34 and having a manufacturers' recommendation as to the number of plows to be used, on an average had 6.9 highest permissible drawbar horsepower per plow.16 Out of a total of 19 tractors, however, 3 had only 5 to 5.99 such horsepower per plow, while 4 had from 7.00 to 7.99, and one had 9.11 such horsepower. For 10 crawlers, the range was from 4.61 to 7.88 highest permissible drawbar horsepower per plow.17 The conception of the amount of power provided per plow is also changing, owing primarily to increases in speed. The fact that increases in speed do not proceed simultaneously for all makes of tractors is a further reason for keeping the assumptions as to the amount of power provided per plow indefinite. Obviously, vague conceptions as to the amount of power necessary per plow cannot be of any great help in power studies in which exactness is indispensable. The handicaps faced by investigators of farm power under these conditions can be easily appreciated. The grouping of tractors by the number of plows used results in great overlapping of the size groups formed. Neither can the investigators rely upon manufacturers' recommendations. For several tractors there are no such recommendations; for many tractors various numbers of plows are recommended, while manufacturers also provide different amounts of power per plow in different models constructed simultaneously, " Manufacturers' recommendations expressed in a range were averaged in making this computation. The highest permissible drawbar horsepower (see p. 24) should not be confused with the drawbar horsepower mentioned above; it will be shown later that several horsepower of different sizes are used for measuring tractor power. " See also Table 3, Part B, in which the power of several tractors on the market January 1, 1937, is given, together with the manufacturers' recommendations as to the number of plows to be used with them (p. 46).

SIZE OF TRACTORS and in models bearing the same name but constructed in different years and differing in construction. The investigator therefore must determine for himself the number of plows each tractor under consideration can draw. Having rejected the number of plows used, because of the unavoidable confusion, the investigator must try to find out the number of plows each tractor model18 is capable of pulling; in other words, he has to create his own "abstract plow." So far as each individual study is concerned, the influence of outside factors (soil cohesion, depth of plowing, and so on) on the grouping of tractors by size usually will not be a disturbing factor when the tractors are classified by the investigators. This is a considerable gain, since the influence of these factors is recognized as highly detrimental to the exactness of the measure.18 But the conclusions of the student may nevertheless be materially affected by the cohesion of soil, the depth of plowing, and similar outside factors in the investigated area. Investigators may also have different ideas as to the best methods of performing farm operations. One investigator may consider fast or deep plowing desirable, and will therefore class a certain tractor as a three-plow tractor; whereas another investigator may class the same tractor as a four-plow tractor. Whatever the reasons, important variations in the designation of tractors do occur in different studies.20 Even with the effect of outside factors partly eliminated, the indefiniteness of the amount of power needed per plow affects strongly both the procedure that can be followed and the inferences that can be drawn. The plow is a very large unit. It equals 100, 50, or 33.3 percent of the power of the three most frequently used sizes of tractors. In statistical analysis, the unit of measurement usually forms a much smaller percentage of the things measured, or else fractions of the unit are used in order to approach more closely the desired degree of exactness. 26

18 Fortunately tractor models are not changed every year, as is the case with automobiles. Nevertheless, omission to include in the questionnaire a query as to the age of the tractor excludes the possibility of correct tabulation. The elimination of these factors makes meaningless the principal reason for the use of the plow as the measure of the power of tractors. " For example, tractors which were considered four-plow tractors by Starch under conditions in Montana were included in the three-plow group b y Reynoldson et al. in their study on power in the C o m Belt.

SIZE OF T R A C T O R S

27

B u t this procedure can be followed only if the measure is exact and otherwise capable of being split into fractions. Investigators can determine the size of tractors only in whole plows (in spite of the fact t h a t manufacturers' recommendations frequently are in two figures). Even if the objection that a plow cannot be split into parts physically were overcome, the extreme vagueness of the amount of power designated by the plow would not permit using fractions of it. Similarly, in tabulations for tractors of different sizes, the power of which is measured in plows, no class interval other than a whole plow or several plows has ever been used. 21 The average power of a particular group oj tractors, under these conditions, necessarily showed considerable divergence in different studies, even when the d a t a were treated correctly. For instance, the first two-plow general-purpose tractor which came on the m a r k e t was rather small, and the earlier studies necessarily considered only this make. Since then, larger generalpurpose tractors, still characterized as two-plow tractors, have been added, the first one being eventually replaced by a model with about 35 per cent more power. Hence a substantial increase must have taken place in the average size of general-purpose two-plow tractors covered by studies during this period. Almost all one, two, and three-plow wheel-tractors placed on the market in the last few years can be had either as four-wheel or three-wheel tractors. T h u s a two-plow ordinary wheel-tractor has the same power as a general-purpose tractor of the same make. Formerly, however, the two-plow and three-plow generalpurpose tractors frequently had less power than similar ordinary wheel-tractors. Consequently, the average size of the generalpurpose tractors now used on farms is likely to be less than that of corresponding ordinary tractors. T h u s comparisons of these two types found in many studies are mostly comparisons of tractors of unequal size. Findings on a plow basis for wheeltractors and crawlers also are not always comparable. T h e same holds true for comparisons of rubber-tired tractors with tractors " Some students t r y t o reduce t h e s h o r t c o m i n g s resulting f r o m t h e large size of the unit of m e a s u r e m e n t a n d of t h e class interval b y such devices as distinguishing light and m e d i u m t w o - p l o w t r a c t o r s ( W r i g h t a n d A y l e s w o r t h , 1934 Tractor Costs on 66 Michigan Farms, p. 3 ) , or t w o - p l o w t r a c t o r s w i t h m o r e t h a n 10 horsepower and o t h e r t w o - p l o w t r a c t o r s ( Y o u n g a n d Collier, op. cit., p. S).

28 SIZE OF TRACTORS of other types, the results being even less reliable than comparisons between crawlers and tractors on steel wheels, or between ordinary steel-wheel tractors and similar general-purpose tractors. The indefiniteness of the plow as the class interval in size group tabulations is apparent if it is compared with the class interval used in dealing with other objects. The usual grouping of a series with a class interval of one unit is: From 0 to 1

or

Over 1 to 2 Over 2 to 3, and so on

From 0 to under 1

From 1 to under 2 From 2 to under 3, and so on

In this case, 0, over 1, over 2, and so on (or 0, 1, 2, and so on) are the low limits of the groups, 1, 2, 3, and so on (or under 1, under 2, and so on) the high limits, and 0.5, 1.5, 2.S, etc., are the mid points. The grouping of tractors on a plow basis, on the other hand, usually takes the following form: Two-plow tractors Three-plow tractors, and so on What are these two-plow and three-plow designations? Mid points or low limits? Logically, they should be considered the low limits of the groups. A tractor which cannot draw two plows without excessive strain should not be included in the two-plow tractor group. Such a conception is clearly accepted only by Young and Collier in the Indiana study. Most investigators, however, include in the higher groups tractors with somewhat less power than is considered necessary for the group. Others go still further in this direction, treating the group designations almost as mid points. In some cases, the two-plow group included even tractors which had not enough power for 1.5 plow, according to the conception prevailing at the time of the investigation.22 When, in farm studies, farms are grouped by size, with the number of acres as the unit of measurement, the results are seldom applied to the mid point of the groups, as, for example, "This has happened particularly with old-model Fordsons. Since the introduction of the "baby" tractors, which are widely used with two-bottom plows, there is great danger that they may be classed in power studies as two-plow tractors.

29 by placing the findings for farms with 80 to 120 acres in a 100acre group. The usual procedure is to compute the real average of each size group. For instance, in the foregoing example, this average might happen to be 96 acres per farm. The next step is to divide the average findings for each group, e.g., the number of man or horse hours per farm, by the average size of the farms, thus determining for each size group the average number of man or horse hours per acre. These data frequently are the only ones of substantial value. Nothing comparable has been attempted by those who use the plow as the measure. Even a computation of performances per plow, insignificant as it would be because of the large size of the plow, has never been undertaken, owing to the difficulties encountered in the use of the plow as the unit of measurement. The use of the plow as the measure of tractor power in power studies does not permit comparisons of findings of studies carried on simultaneously, and much less of findings of studies made at different times. Neither does the use of the plow permit comparisons of findings of the same study for different types of tractors. Even within each type group, the analysis cannot proceed along lines which promise trustworthy conclusions. Plowing is admittedly a very important operation. Nevertheless, is it reasonable, for the sake of this one operation, to present the data for all other operations in a confused way, especially when the number of plows that are pulled, or can be pulled, by tractors does not convey exact knowledge even about plowing itself? SIZE

OF

TRACTORS

T H E H O R S E P O W E R AS T H E M E A S U R E OF TRACTOR P O W E R T H E RATING OF TRACTORS 2 3

The horsepower, equivalent to 550 foot pounds per second, is a definite unit, like a pound, a mile, or an acre. All kinds of engines, when bought, sold, or investigated, are dealt with on the basis of horsepower. One might expect, therefore, that this same measure, to the exclusion of all others, would be applied to trac" The rated power is the power the tractor is supposed to be able to develop permanently. It is used in business transactions, studies, and so on, for designating the power of tractors. Moreover, when one says "belt horsepower" or "drawbar horsepower," "rated belt horsepower" or "rated drawbar horsepower" is meant. When maximum belt or maximum drawbar horsepower is referred to, it always is mentioned specifically.

30 SIZE OF TRACTORS tors. The horsepower, however, has not acquired universal significance in this field, either in the trade or in tractor studies. It is noteworthy, in fact, that the application of the horsepower as a measure for tractors has shown a sharp decrease. Several years ago, it was common practice to include figures indicating the horsepower, in names of tractors. 21 It is less often done now.25 As figures on the horsepower came to be omitted, the buyer or other interested person was not always given comparable information in another form. In recent years, it is true, the horsepower in the form of the highest permissible drawbar ratings (see p. 33), again more frequently finds its way into the advertisement literature. 26 What is the reason for this surprising deviation from the procedure followed with respect to other mechanical sources of power? The answer is: the indefiniteness of the horsepower as this term is used in connection with tractors. The horsepower, it is true, in itself is definite. It becomes indefinite when applied to tractors because of the lack of agreement about what is to be expressed in terms of horsepower. While the maximum power of the tractor usually is known, its use is very seldom attempted, since, in the nature of the case, it is impossible to utilize the maximum power of the tractor in farm work, even for very brief periods of time. Moreover the maximum power which is used as the basis for computing the power of tractors is an imaginary figure. It is arrived at by correcting the result of a test, made at a carburetor setting giving maximum power at rated engine crankshaft speed, to standard normal temperature and standard barometric pressure at sea level. The maximum power which the same tractor develops under average " Usually two figures, for instance, 10/20, have been used. The first one is supposed to represent the rated drawbar horsepower and the second one the rated belt horsepower. If investigators of farm power use only one figure for designating power, probably always rated drawbar power is meant. Manufacturers, however, when giving one figure usually have belt power in mind. Yet sometimes their figure lies between the rated belt and the rated drawbar power. 15 So far as such figures are still in use, they do not always refer to the power of the tractor. Since figures appearing in the names of tractors, by their size and form of presentation, may easily be taken as referring to the power of the tractors, the confusion, which is already great owing to the different ways of designating power (see the preceding note), is increased still more. " A s late as 1935, however, the Bureau of Labor Statistics shifted its statistics of wholesale prices of wheel tractors from the horsepower basis to the basis of the number of plows (see p. 60).

SIZE OF TRACTORS 31 atmospheric pressure and at average temperature, and with the carburetor setting recommended by the manufacturers for work on farms, is always less, the difference amounting to from 5 to 10 percent and sometimes even more. Moreover, tractors, when tested, are in perfect or practically perfect condition, while tractors used on farms are more or less worn. Owing to the rather limited capacity of tractors for overloading, it is likewise very difficult, and in certain conditions impossible, to make full use of the maximum power which a certain tractor can develop under the actual atmospheric pressure, at the actual temperature, and with the actual carburetor setting. Experience demonstrates that only about SO percent of the theoretical maximum drawbar power (established maximum power, corrected to standard temperature and atmospheric pressure) of tractors with steel wheels is used in field work.27 Thus a tractor with a theoretical maximum drawbar power of about 18 horsepower performs, under rather favorable conditions, the work of only about eight to nine horses of average weight and age for the Corn Belt.28 However, only the power which can be developed permanently in field or belt work, or even perhaps only the power which, under average conditions, is developed in this work, is important for the farmer. The rated horsepower, therefore, is established at some reduction from the maximum horsepower. The extent of the needed reduction, however, is a matter of opinion. The arbitrary factors involved in determining the ratio of the rated tractor power to the maximum power introduce into the horsepower, as the measure of tractor power, the same variability and indefiniteness that is typical of the "plow." The great divergency in manufacturers' ratings of tractor power has given trouble from the time tractors were first put on the market, leading to urgent requests for standardization. In 1919 the state of Nebraska passed its Tractor Law. In 1920 11 Experiments made in Canada in farm conditions indicate a somewhat higher percentage. See Robson and Shanks, "The Efficiency of Use of Farm Power." But "the season was hot and unusually dry, thus resulting in higher draft for plows and lower draft for such implements as combine" (p. 565). Moreover, the authors may have used in their computations the actually developed maximum power rather than the maximum power corrected to normal temperature and normal barometric pressure. " The performances of these horses probably average about one horsepower unit.

32

SIZE OF TRACTORS

official tests were begun at the University Farm, Lincoln, Nebraska, tests at maximum belt and drawbar power and at rated (manufacturers' ratings) belt and drawbar power being made. In 1920, also, the American Society of Agricultural Engineers and the Society of Automotive Engineers adopted the CHART 1 MANUFACTURERS' RATINGS OF DRAWBAR HORSEPOWER EXPRESSED IN PERCENT OF MAXIMUM DRAWBAR HORSEPOWER Based on fifty-eight tractors tested in Nebraska in 1920 NUMBER OF TRACTORS PERCENT

6

8

10

12

14

50-54.9 55-59.9 60-64.9 65-69.9 70-74.9 75-79.9 60-64.9 85-69.9 90-94.9 95-99.9 N0 100 ' u u O*VER

SOURCE: HEBRASKA

TRACTOR

TESTS

Manufacturers' ratings of the drawbar power of four tractors amounted to less than 60 percent of the maximum drawbar power of these tractors. On the other hand, five tractors were rated by their manufacturers at more than 90 percent of the latter. Only 24 percent of the tested tractors were comprised in the central group containing the tractors whose rated power equalled 75 to 80 percent of maximum power. Hence, manufacturers' ratings evidently did not provide an adequate basis for comparing the power of different tractors.

recommendation that the rated belt and rated drawbar power should not exceed 80 percent of the maximum power.29 In 1925 these organizations increased to 90 percent the ratio of the rated belt power to the maximum belt power. The Farm Tractor Rating Code of the A.S.A.E. and the S.A.E. in its present form " As stated above, the maximum power used for computing the rated power is the maximum power which would be developed by the tractor at normal temperature and normal atmospheric pressure, and with a carburetor setting giving maximum power at rated engine crankshaft speed.

SIZE OF TRACTORS 33 recommends as the minimum reduction from the maximum power IS percent for belt and 25 percent for drawbar power. In other words, the highest permissible ratings under this Code are 85 percent of the maximum horsepower for rated belt horsepower and 75 percent of the maximum for rated drawbar horsepower. Complaints about extreme variations in manufacturers' ratings were fully substantiated when checked in Nebraska. Even models of the same manufacturer showed wide divergences in rating. Chart 1 presents the results of tests of fifty-eight farm tractors listed in the 1921 Cooperative Tractor Catalogue. The manufacturers' drawbar ratings are expressed in percentages of the maximum drawbar power, as ascertained by the official tests. It will be observed from Chart 1 that the ratings indicated by manufacturers ranged from only half of the maximum power to more than the maximum power. According to O. W. Sjogren, out of sixty-five tractors tested in Nebraska in 1920, the manufacturers' belt rating was in one case less than 70 percent of maximum; a relation of 70.1 to 80 percent, 80.1 to 90 percent and 90.1 to 100 percent was found in 21, 22, and 23 cases respectively. For seven tractors, the rated belt power as given by the manufacturers was higher than the maximum belt power of those tractors. 30 The initiation of the official tests and of the rating rules of the A.S.A.E. and S.A.E. was a significant step toward attaining uniformity in the rating of tractors. The Nebraska testing organization has acquired a world reputation and has been duplicated in several countries. Yet not all obstacles were overcome at once. The tractor was being rapidly improved. Models of tractors replaced one another in quick succession. The power of tractors changed. Their efficiency, particularly the relation of drawbar to belt power, increased most notably. While at first the drawbar power of wheel tractors usually amounted to about 50 percent of the belt power (here is the origin of the usual designations of tractors as 10/20, 15/30, and so on), this ratio increased to 60 percent and more. Many manufacturers, however, did not wish to change their ratings, which had become part of K

"Tractor Testing in Nebraska." See also the paper of the same a u t h o r : " W h y Standardize Tractor Ratings?" presented to the annual meeting of the American Society of Agricultural Engineers.

34 SIZE OF TRACTORS the trade names of their tractors. Yet the tests in Nebraska at rated load for many years were made at manufacturers' ratings. The official tests, therefore, could not prevent confusion. For instance, two different models of a tractor having a manufacturers' rating of 15/27 were tested in 1924 and 1927. The maximum belt horsepower increased from about 33 to nearly 40: the maximum drawbar horsepower advanced from about 23 to nearly 30, but the rated belt and drawbar horsepower remained unchanged. Many other tractors showed similar increases in power without a corresponding change having been made in their rating by the manufacturers. At the beginning of the 1928 testing season, the rule was introduced in Nebraska that if tests should show the manufacturers' ratings to exceed the highest permissible ratings under the Tractor Rating Code, attention should be called to this fact in the official report. Another change has been even more important. When manufacturers have not rated their tractors, the tests at rated load have been made in Nebraska at about the highest permissible rating under the code. Gradually manufacturers began to omit their own ratings, and finally practically discontinued the practice. Beginning with 1930, the highest permissible ratings under the code are being established in Nebraska for all tested tractors, whether they are rated by manufacturers or not. The Tractor Rating Code and the Tractor Testing Code have finally been linked together by this action.31 A few examples of recent models of tractors will show how significant this change is. Two tractors of the same type and produced by the same maker were sold under the designations "25" and "50" respectively. If no other source of information than these figures were available, one would naturally assume that the power of the second tractor was twice that of the first. " Beginning with 1935 the results of maximum load tests, made for establishing the highest permissible ratings, are included in the reports of the Nebraska Department of Agriculture. In earlier years this was not done, and some misunderstanding resulted. There is still room for improvement in the procedure of tractor testing, however. For example, the rated drawbar test is made at a speed "designated by the manufacturer as the most suitable for plowing or ordinary farm work." But some manufacturers choose so high a speed that it cannot be maintained in farm operations, and this, apparently without encountering objections.

SIZE OF TRACTORS 35 The established highest permissible drawbar rating of the "50," however, was higher than that of the "25" only by 76.5 percent, according to the Nebraska tests. For two tractors of another manufacturer, designated as "30/45" and "15/25" respectively, the relationship in drawbar horsepower proved to be, not 200 to 100 as would be expected from the designations, but only 170.7 to 100.32 So far as belt power is concerned, it must be admitted that, contrary to what was true of manufacturers' ratings, in the highest permissible ratings as established in Nebraska a comparable measure for the power of all tractors has become available. For drawbar power, however, this is true only for tractors of the same types. It was shown on page 10 that crawlers perform more work per maximum drawbar horsepower than tractors on steel wheels. The greater adhesion of the crawlers to the soil makes possible the use of a higher percentage of the available drawbar horsepower than is possible in the operation of tractors with steel wheels. Since the rating of tractors is intended to indicate the portion of the maximum power which a tractor can be expected to develop under average farm conditions, the highest permissible ratings of crawlers should be higher than those of similarly powered tractors with steel wheels. Establishing the same limits for the highest permissible drawbar ratings of tractors with steel wheels and for crawlers does not conform to the character of their service on farms. Inasmuch as more recently manufacturers' ratings of the most widely distributed tractors used to be considerably under the highest permissible ratings, the use of the highest permissible ratings instead of the manufacturers' ratings involves the danger of confusion. This risk is present particularly when tractors for which the highest permissible ratings are es" The computation of the work done by tractors per drawbar horsepower was necessary {or many of the interesting problems discussed in the recently published study, The Economic Relation oj Tractors to Farm Organization in the Grain Farming Areas oj Eastern Washington by Landerholm, especially for the proper estimation of the "relation of tractor size to efficiency." Unfortunately, the drawbar horsepower assigned to the tractors investigated w a s not always on a comparable basis. For example, the drawbar power of the "50" tractor mentioned in the text w a s assumed to be twice the power of the "25" tractor. T h e results of comparisons of efficiency, which proved rather unfavorable for the "50," probably originated in the indicated difference between the actual and the assumed power of those tractors.

36 SIZE OF TRACTORS tablished and those without these ratings are dealt with simultaneously. For instance, the above-mentioned (see p. 34) tractor with nearly 30 maximum drawbar horsepower and nearly 40 maximum belt horsepower was for many years sold as a 15/27 tractor, although the highest permissible ratings under present rules would have been about 22/33. The general-purpose tractor of the same make, introduced later, when tested in Nebraska received the highest permissible drawbar rating of IS.5 horsepower, i.e., even a little higher than the rating of the other tractor. The corrected maximum drawbar power as ascertained in Nebraska, however, was 20.7 horsepower for the general-purpose tractor, as against 29.4 horsepower for the 15/27 tractor, indicating that the power of the 15/27 tractor was about 40 percent greater than the power of the generalpurpose tractor. The makers themselves recommended three to four plows for the first tractor and only two for the second. Makers of a 15/30 tractor changed the model of this tractor in 1929. The new model had about 15 percent more drawbar power than its predecessor. It was, however, rated as 22/36, close to the highest permissible ratings. Thus, the nominal increase in drawbar rating was about three times the real increase. Usually the changes resulting from making the rated tests at the highest permissible ratings may be demonstrated on the average number of plows pulled by the tractors. It has been stated that, according to common opinion, about 5 drawbar horsepower per plow are necessary. This figure was fixed at the time when manufacturers' ratings were in general use. On the basis of the highest permissible ratings, wheel-tractors have, on the average, 6.7 horsepower per plow. Even for crawlers, the average highest permissible drawbar rating (5.5 horsepower) is 10 percent higher than tractors are expected to have.33 Until the public has learned to distinguish between the old and the new ratings, misunderstandings and dissatisfaction are inevitable. T H E HORSEPOWER I N POWER STUDIES

In view of the existing confusion with regard to the power of tractors when it is determined in terms of horsepower, it would " A portion of the difference, it is true, is the result of an increase in the amount of power provided per plow, since the time when the idea of 5 drawbar horsepower per plow became established.

S I Z E OF

TRACTORS

37 have been a miracle if investigators of tractor power had always been successful in their treatment of the horsepower of the tractors investigated by them. It was inevitable that larger tractors were often placed in lower power groups, while smaller tractors were put into the higher groups. 34 The confusion occurred especially in the case of tractors which, in spite of changes in power from year to year, went on bearing the same names. T h e age of the tractors was not always asked for, and, when asked, was not always known by the owner. T h e damage to the comparability of different studies was even more severe. With information on the horsepower of the investigated tractors rather vague, investigators using the horsepower as the measure of the power of tractors were in a situation similar to that of the investigators preferring the plow as the measure. T h e horsepower as the measure also would not permit of adequate statistical treatment. T h e investigators, for example, were compelled to be satisfied with grouping the investigated tractors into 10/20, 15/30 (and so on) groups, strikingly resembling the usual grouping in two-plow, three-plow (and so on) tractors. T h e 10/20 tractor would correspond to the two-plow tractor, the 15/30 tractor to the three-plow tractor, and so on. As is the case with groupings on the basis of "plows," the class interval and the unit practically coincided in the groupings on the basis of horsepower, the well-known five horsepower being both the class interval and the unit. T h e rated drawbar horsepower is nearly equivalent to the power of a horse, and even a decimal of a drawbar horsepower corresponds to dozens of acres in wheat. Yet, so far as the writer is aware, only one attempt has ever been made to compute the average power of a given group of tractors or to make calculations per horsepower in the same manner as they are made per horse, or per crop-acre, and not with complete success (see footnote 32 to this chapter). 3 5 As in the case of the plow, it is usually not known whether " Even in Murdock's expert study on Mechanical Tests on Tractor Farming Equipment, tractors with ratings very close to the highest permissible ones occasionally were treated on the same basis as those for which the rated power was much smaller than the highest permissible one (see Table 6 of that study). " Since the plow as the measure of power also is indefinite, computations per plow are never found in studies on tractor power, although computations of this type constitute a necessary part of practically all farm management studies.

SIZE OF T R A C T O R S 38 10/20, 15/30, and so on, horsepower are the low limits of the groups, their mid points, or whether these ratings lie somewhere between the two. Great uncertainty prevails in this respect. For example, it is probable that an investigator who hesitated to include a tractor with 9 drawbar horsepower in the 10/20 group may have placed tractors with 13.5 and perhaps even with 13 drawbar horsepower in the 15/30 group. Thus everything that has been said about the way in which investigators have been compelled to use the "plow" as a measure applies to the horsepower as well. Using the horsepower instead of the "plow" did not increase precision, so long as the effort to secure exactness in designating power in terms of horsepower was unsuccessful. 30 Moreover, the indefiniteness of the horsepower for measuring tractor power and the inevitable confusion arising therefrom was, in truth, so great that most investigators considered even the very indefinite "plow" to be more definite than the horsepower and in time ceased to use the latter. 37 SUGGESTIONS T H E U N I T OF M E A S U R E M E N T

From the foregoing presentation, it is evident that the "plow" cannot be used as an accurate measure of the power of tractors in power studies. Only an exactly determined horsepower may, it is hoped, provide an adequate unit for this purpose. We do not give much weight to the argument that the farmer will not understand this unit and that he may confuse horsepower in tractors with the power of a horse. Through threshing operations, farmers are well acquainted with the meaning of the term horsepower. All tractor owners also know the given " A n interesting example of the struggle to attain the highest possible exactness under the prevailing conditions was set by Young and Collier in their study on Labor and Power Used in Crop Production in Central Indiana. In Table 2 of that study, for example, tractors with less than 10 horsepower, other twoplow tractors, and three-plow tractors are distinguished. By using simultaneously the plow and the horsepower as measures, the authors succeeded in eliminating considerable confusion arising from the inclusion of small tractors in the twoplow group. " T h e Bureau of Labor Statistics recently revised its series of wholesale prices of agricultural machinery, and took the opportunity of shifting from a designation in horsepower to that iri number of plows (see p. 60).

SIZE OF

TRACTORS

39

ratings of their tractors, though unfortunately these ratings are not always correct. It is perhaps easier to sell a tractor to a farmer on the basis of so many plows than on the basis of so many horsepower, but investigators have to concentrate on clarifying the role of tractors on farms, and this can be done only by using the horsepower as the basis of measurement. Since the drawbar and not the belt work is the primary performance of farm tractors, the drawbar horsepower is preferable to the belt horsepower as the basic measure of power. In comparing the findings for wheel-tractors with those for tracklaying tractors, it would, of course, be necessary to take into consideration the fact that tracklaying tractors have less belt horsepower per drawbar horsepower, and still less per adjusted horsepower,38 than have wheel-tractors. To get correct results, additional computations may be necessary in some cases. It has been pointed out above that the highest permissible ratings under the recommendations of the A.S.A.E. and the S.A.E. Tractor Rating Code do provide a comparable basis for the belt power of all types of tractors and for the drawbar power of the same types of tractors. For tractors tested in Nebraska, in 1930 and later, the highest permissible ratings are shown in the reports issued for each tested tractor and in the yearly reports entitled Nebraska Tractor Tests, 1920 to 19. .. For practically all tractors tested before 1930, the highest permissible belt and drawbar ratings have been computed in Appendix I, in accordance with the advice of experts. For this purpose the code formula for correcting to standard temperature and barometer readings was applied to the horsepower as ascertained in Nebraska at the maximum load test. For tractors tested in 1928 and 1929, an adjustment in carburetor setting, in direct proportion of 100 to the setting recommended by the manufacturer, also has been made. So far as available, the results of maximum tests, in the gear in which the rated drawbar test was made, have been used for these computations. The findings are reduced to highest permissible ratings by deducting 15 percent (belt power) and 25 percent (drawbar power). The ratings established in Nebraska in tests made in 1930 and later also may be found in Appendix I. * Concerning the adjusted horsepower, see p. 41.

40

SIZE OF

TRACTORS

The progress attainable by a universal utilization in power studies of the highest permissible ratings would be great, even if no additional improvements were made. It is, however, an easy matter to introduce a further refinement. Two points should be considered in this connection. 1. It was shown that the highest permissible ratings under the Tractor Rating Code usually are higher than the ratings previously employed by manufacturers of the widely used tractors with which the public has become acquainted. This is particularly true as to wheel-tractors, manufacturers' ratings for crawlers being considerably nearer to the highest permissible ratings.38 2. The highest permissible drawbar ratings may be used as the basis for comparisons only for the same types of tractors. In order to bring the highest permissible drawbar ratings of tractors with steel wheels down to the equivalent of five drawbar horsepower per plow—the measure to which farmers are accustomed—their reduction by some 30 percent would be required. For crawlers the necessary reduction would amount to about 10 percent.40 These reductions would be strongly resisted by the manufacturers. It would therefore be advisable, perhaps, to abstain from any reductions of the highest permissible ratings for crawlers, and to make a reduction for wheel-tractors only so far as it is necessary for bringing the performances of these tractors per drawbar horsepower in line with the performances of the crawlers.41 " This is hardly haphazard, but probably is made in view of the greater amount of work performed by crawlers per maximum drawbar horsepower. 40 It would perhaps be desirable to reduce the drawbar horsepower of tfactors to a level which would make the performances of tractors per rated drawbar horsepower and those of horses about equal. Had this been done, comparisons between the cost of tractor power per rated drawbar horsepower hour and that of a horse hour would not be misleading, as they now are. See the comparisons made by Hurst and Church, Power and Machinery in Agriculture, pp. 26-27; and those of Blasingame, "Relation of Mechanical Progress in Agriculture to Land Utilization and Land Policy," Part I, Supplementary Report of the Land Planning Committee to the National Resources Board, p. 40. T h e highest permissible ratings of wheel tractors would have to be reduced by about 35 percent in order to make the performance of a drawbar horsepower about equivalent to that of a horse of average size in the Corn Belt. u It is probably not superfluous to point out that a reduction of the highest permissible ratings is not contrary to the rating code. As shown by the expression "highest permissible," the A.S.A.E. and the S.A.E. do not attempt to recommend ratings for general use. T h e y merely wish to establish an upper limit for the ratings of the manufacturers.

SIZE OF TRACTORS 41 As indicated above (page 11), it is beyond the power of the present writer to ascertain the exact difference in performances per drawbar horsepower between crawlers and wheel-tractors. As a preliminary estimate, the performances in field work of tractors with steel wheels per drawbar horsepower may be assumed to be smaller by about 20 percent than similar performances of crawlers. Hence the highest permissible drawbar power for tractors with steel wheels, reduced by 20 percent, is designated as adjusted drawbar horsepower, or simply adjusted horsepower for this type of tractor. For crawlers, highest permissible drawbar ratings and adjusted ratings coincide. It may be pertinent to emphasize the fact that the established relationship between the adjusted horsepower of tractors with steel wheels and that of crawlers is roughly valid only for drawbar work. It can be applied to the total farm work only if no belt work has to be done by crawlers, which is usually the case in this country. Relatively few crawlers are used on farms that do not harvest their grain with the combine, and therefore do not require any belt work. For regions in which crawlers also are used for belt work, the relationship in power between tractors with steel wheels and crawlers must be established for each particular case separately. Tractors with steel wheels are the predominant type of tractor. It is therefore desirable always to use for them an adjusted horsepower of the same size. Hence in cases when crawlers are also used for belt work, for this type of tractor too the adjusted horsepower has to be established with some reduction from the highest permissible ratings. The reduction must be so arranged that for the weighted average of all performances of both types of tractors, the adjusted horsepower of crawlers is equal to the adjusted horsepower for tractors with steel wheels, established at 20 percent under the highest permissible drawbar ratings. THE CLASS INTERVAL

If a definite measure of power has been established, the class interval obviously also has to be determined in the same measure. Computed in adjusted horsepower, the class interval will possess all qualities necessary for proper statistical analysis. So far as the unit of measurement is concerned, no difficulty would be found in subdividing the class interval into as small fractions

42 SIZE OF TRACTORS as would be found necessary. The average number of adjusted drawbar horsepower per tractor in each group could be readily computed, and the relation of one tractor group to another would become reasonably definite. For example, when employing the usual procedure, one assumes that the power of threeplow tractors is larger by 50 percent than the power of two-plow tractors. With the class interval proposed for tractors with steel wheels (see pp. 43-46), the computation might yield an average of 16.5 and 12 adjusted horsepower respectively, or an actual ratio of 137.5 to 100, instead of 150 to 100. Findings of studies made in different states and countries, as well as of those made at different times, will be comprehensible, and their comparisons become valid, if the class interval is determined in definite horsepower. In the interest of precision, some computations could be made per adjusted drawbar horsepower, as they are now made per crop acre, per horse, and so forth. It has been indicated above that both plow and horsepower, when used for the grouping 100 100

W\ \

90

\

^ 3-4 piow

S

I \

\

\

\

\

80

Ci awler

\

v

•—>

V . X\

\

N. ,

70

60

- -

• ••

1926

1

1928

1

1930

1

1932

1

1934

1

1936

The three-to-four-plow tractor is a tractor with steel wheels. The considerably greater decline in the price of crawlers in the last decade materially increased their power to compete with tractors with steel wheels.

It is the most convenient and therefore the usual practice to employ as first cost the price at which the present owner or his predecessor bought the tractor when it was new. This procedure, however, has not always conformed to the requirements of reasonable reliability, owing to extensive changes in the prices of tractors. The wholesale prices of the Bureau of Labor

60 METHODS OF COMPUTING COST Statistics are the only available price series for tractors. Before 1935, the Bureau published prices of a 10/20 tractor, extending the series back to 1913. From the preceding discussion (pp. 36-38) it is evident that a price series of goods so indefinitely described was unlikely to be adequate. On the occasion of a general revision of the price series of farm machinery in 1935, the Bureau shifted from the indefinite designation 10/20 to the obviously incorrect designation by numbers of plows, series of prices of two-plow and three-to-four-plow wheel-tractors being substituted, and likewise carried back to 1913. As the power provided per plow has been increased by about 75 percent since the World War, the prices (and the index based thereon) would be unusable if in each particular year they referred to the tractors then designated as two-plow or three-to-four-plow tractors. Fortunately these designations have not been taken too seriously.1 The prices in the earlier years have been so adjusted as to refer rather to present ideas of what amount of power is necessary per plow than to the conception prevalent at that time.2 Still, the decline in prices of wheel-tractors during the last fifteen to twenty-five years was considerably larger than that reflected in the official indices. The new price data of the Bureau of Labor Statistics include also a price series of a crawler (without any specifications as to size). The prices before 1925 are evidently unusable, the index showing an increase of the prices of crawlers by 31 percent from 1921 through 1925, in the face of a decline in prices of wheel-tractors by 28 to 34 percent during the same years (actually the prices of crawlers also declined slightly). 3 The major changes in the nominal prices of tractors, as indicated by the price index of three-to-four-plow tractors compiled by the Bureau of Labor Statistics, were as follows: After an 1

The same was true for the designation 10/20 used by the Bureau previously. ' T h e Bureau of Labor Statistics gives as the average wholesale price of the three-to-four-plow tractor $1,564 in 1919 and $1,556 in 1920. The average retail price, f.o.b. factory, of four widely used tractors (two sold as three-plow, one sold as three-to-four-plow, and one sold as four-plow) on April 1, 1920, was $1,518, according to the Cooperative Tractor Catalogue. * Considering the extremely inexact character of the prices, one is somewhat surprised to see them being quoted in tenths of a cent. The price of the twoplow tractor in 1913, for pxample, is given as $1,361,333, while the figure comparable to the prices quoted by the Bureau for recent years might have been $1,500 or even substantially higher.

METHODS OF COMPUTING COST 61 increase from 144.9 in 1913 ( 1 9 2 6 = 100) to 187.4 in 1918, the index went down to 96.2 in 1928 (with an intermediate increase in 1921). Prices remained unchanged for the ensuing three years. From 1931 to 1933, the index again declined to 84.7. The succeeding recovery was limited to an increase to 87.7 in 1936. Prices of crawlers declined much more in recent years. From 111.7 in 1925 and 100 in 1926, the index went down to 67.9 in 1934. In 1936 the prices still were almost 30 percent below those of 1926. The prices of the individual tractors included in studies are usually merged in averages. It is therefore difficult to decide whether harm has been done by employing prices which have lost their economic significance. Fortunately, Schwantes and Pond4 have provided us with very interesting data in this respect. The prices of the three-plow tractors included in their study showed a range from $800 to $2,400. The average price was $1,419 for the obsolete models and $1,265 for the current models. The variations in the prices of wheel-tractors in the last fifteen years were too small to warrant the expenditure of the time requisite for making adjustments for price changes. But the decline of prices of crawlers from 1925 to 1936 has probably been too large to be ignored safely. Failure to consider the price changes of crawlers may impair comparisons of the cost of power of crawlers not only with the cost of horse power, but also with the cost of power of other tractors, the first cost of which has declined much less than that of crawlers. It is suggested that in studies which include tractors bought at significantly varying price levels, the price of the year of survey be used for all tractors regardless of the price at which each particular tractor was bought. These changed prices may be called adjusted first cost or adjusted prices. Some difficulties may be encountered with regard to tractor models withdrawn from the market, as well as tractors bought secondhand. The prices of models withdrawn from the market could be determined by raising or contracting the prices paid for them, in proportion to the change in the index of tractor prices of the Bureau of Labor Statistics. The prices of tractors bought sec4

The Farm Tractor in Minnesota,

p. 29.

62 METHODS OF COMPUTING COST ondhand could be adjusted similarly by using the same proportion of the first cost of the respective tractor in the year or years of survey, as existed between the price of the secondhand tractor to its first cost when purchased by the present owner. The changes in prices of other machinery which are due to improvement in production technique will hardly be so important as to require special consideration in power studies. Machinery is found on tractor farms as well as on horse farms, and there is little likelihood that the machinery of some group of farms is bought at a price level materially different from that of another farm group. Should this occur, however, an adjustment similar to that made for the first cost of tractors ought to be made. DEPRECIATION

Farmers are asked to state the number of years a machine has been used already, and how many more it probably will be used, according to their experience. This provides the so-called estimate of probable life. By dividing the first cost of the machine by the average estimate of life, the yearly depreciation is determined; and from the yearly depreciation the depreciation per day or per hour of use is computed. This so-called straight-line method, based on farmers' estimates of life, is chiefly used by investigators for computing depreciation of general farm machinery. The same method was adopted when tractors, as well as trucks and automobiles, were introduced on the farm. Another method of calculating depreciation which is sometimes employed in power studies is the inventory method. The farmers are asked to state the value of their tractors at the beginning and at the end of the year of survey. The difference between the two values is the depreciation for the year. Depending upon the method used, surprisingly different results are obtained. This can be shown on a comparison of the data of the Missouri study by Smith and Jones, which employed the straight-line method based on farmers' estimates of life, with the data of the New York study by Gilbert, which used the inventory method. In the Missouri study, 33 cents per hour of operation was charged for depreciation, interest, insurance, and taxes to two-plow tractors which on an average were two years

M E T H O D S O F C O M P U T I N G COST 63 old. Gilbert computed the charge for depreciation and interest for tractors of about the same age at 41.7 cents. As against 39 cents per hour of operation for depreciation, interest, insurance, and taxes, charged to old-model two-plow tractors averaging 8.3 years in the Missouri study, only 14.5 cents was charged for depreciation and interest of tractors of about the same age in New York state. The difference between the two sets of figures is so great that, provided the profit or loss from operating tractors as compared with horses is small, an arbitrary choice of one of these methods of computing depreciation may change the results from favorable to unfavorable for tractor use, and vice versa. Divergent results may occur still more frequently if a comparison is made between groups of farms with different kinds of tractors rather than between horse and tractor farms. The need for a more adequate method of calculating depreciation of farm tractors is felt in many quarters. The present writer made his first attempt in this direction in his investigation, Der Schlepper in der Landwirtschaft. A similar effort was made at about the same time by Grest, in Canada. 5 The problem of depreciation may conveniently be treated in two sections: first the more general question of computing depreciation will be discussed and then the methods of determining the duration of life and the total work of tractors will be dealt with. Main factors affecting depreciation.—In order to compute the rate of depreciation of a given tractor in a given year, two things are needed. The investigator has to know the total life of the tractor at different amounts of annual use and he needs a formula expressing the distribution of the total depreciation charge over the life of the tractor. The length of life is dependent on three factors: wear independent of use, obsolescence, and operation. Persons estimating the life of tractors, whether conscious of it or not, usually take two and sometimes all three of these factors into consideration. If the investigator is satisfied with an average yearly rate of depreciation, the formula is 100/n, n being the duration of useful life in years. A correct method of computing depreciation, however, must take into consideration the fact that the '"Comments on Depreciation and Repairs of Combine Harvesters and Tractors on the Canadian Prairies."

64

METHODS OF COMPUTING

COST

value of the service of tractors declines as time goes on. All three enumerated factors, wear independent of use, obsolescence, and operation, exert their effect on the tractor from the very day it is bought. It seems, therefore, justified to offset the lesser value of the service in the later years of the life of the tractor by a reduction of the charge to depreciation. In the first years of its life, the tractor then has to bear correspondingly heavier charges. In that case a more complicated formula, or method, than that given above becomes necessary. DURATION OF LIFE. If an unused tractor were kept perfectly preserved, it would last practically indefinitely. This, however, is never done. Air, humidity, and rain take their toll from a tractor, whether it is used or not. Moreover, after a few years, the tractor, whether it has been perfectly preserved or not, becomes obsolete owing to improvements in tractor construction. The fact that obsolescence and wear independent of use terminate the useful life of tractors is not only taken into consideration but is usually given so much weight that some investigators deem it advisable to base the depreciation charge entirely on these factors, by placing the life of all tractors at the same figure. As the effect of obsolescence on the duration of life is similar to that of wear independent of use in that it ends the life of a tractor after some years whether the tractor is used or not, both factors for convenience usually are combined in providing for depreciation. This procedure is also followed by the present writer. The joint provision for both factors, however, involves the danger that their different properties may be overlooked. Obsolescence, as a factor affecting the rate of depreciation, differs from wear independent of use in that its influence decreases progressively with the increase in perfection attained in tractor construction. The theoretical segregation of both factors, consequently, is significant. Opinions as to the effect of operation on the life of agricultural machinery are not unanimous. According to Davidson, of the Iowa Experiment Station, 6 "the survey revealed that the life of most farm machines is almost entirely unrelated to the * Life, Service,

and Cost of Scrvicc

of Farm Machinery,

p. 263.

METHODS OF COMPUTING COST 65 amount of work performed each year." On the other hand, Smith and Jones found7 that for some kinds of machinery this relation does exist. For mowers, sulky rakes, sweep rakes, corn planters, corn cultivators, corn binders, ensilage cutters, and grain binders, a day's use increases the annual depreciation rate by from 0.11 percent of the initial cost in the case of corn cultivators to 0.45 percent of the initial cost in the case of corn binders. For grain binders the increase in the depreciation rate has been calculated at 0.18 percent of the initial cost, for each additional day of use.8 The major reason for the failure of some investigators to consider the influence of operation on the life of general agricultural machinery is, to be sure, the difficulty of segregating the effect of this factor from that of other more important factors. In addition, the difficulties of ascertaining the differences in the extent to which each of the many machines found on farms have been used probably also acts as a deterrent. In any case, when the problem involves more expensive machines, the effect of operation on the length of life is indicated much more frequently, even if the machine is used for a relatively short time during the year and if the differences in the amount of use are not greater than in the case of less expensive machinery, for which this factor could not be discovered. The authors of the study, The Combined Harvester-Thresher in North Dakota,9 state: "The life of the combine, windrower, and pick-up is affected by the acres harvested [italics by the present writer], crop, soil and topographic conditions." In obtaining the data on husking corn with pickers in Illinois,10 the farmers were asked to state their opinion as to the probable life of corn pickers, both in total acres of corn and in years. The answers evidently so stressed the importance ''Power, Labor, and Machine Costs in Crop Production, Linn County, Missouri, 1910, pp. 21-24. 8 That the depreciation rate is so much higher for corn binders than for grain binders may perhaps be explained to some extent by the fact that the range in annual use has been 1 to 24 days per year in case of the investigated corn binders and only 3 to 13 days in case of grain binders. The wider range of use in the case of corn binders made it easier to separate the effect of use on the life of the machinery from other factors having a similar effect. ' Benton et al., p. 44. 10 Johnston and Myers, Harvesting the Corn Crop in Illinois.

66 METHODS OF COMPUTING COST of acres harvested that the following formula was used in the investigation for calculating the yearly depreciation: Cost of picker X acres husked per year Average number of acres picker can husk during life Each piece of so-called general machinery has, with a few exceptions, a specialized job to perform, while the tractor, not belonging to general machinery, is used with most of them. Hence the total annual use of the tractor usually is many times greater than that of any other important agricultural machine. Consequently even if it could be shown that operation does not greatly affect the life of general machinery, this fact would not necessarily be true of tractors. A study of the information procured from farmers reveals that in many cases farmers are prone to acknowledge the fact that the amount of work done by a tractor has a great effect on the length of its life. The estimates of life for 120 two-plow tractors in Missouri11 varied from 11.6 to 4.7 years for tractors used from 200 to 1,600 hours respectively in the year of the investigation (see Appendix II, part A). In Minnesota 12 the variations were from 7 years for tractors used 1,000 and more hours in the year of investigation to 12 years for tractors used less than 200 hours in the year of investigation. Starch13 goes furthest toward acknowledging the effect of operation on depreciation. He does not consider any other factors, computing depreciation solely on the basis of hours of operation for tractors, and on acres covered for all other agricultural machinery. 14 Thus operation has to be accepted at least as one of the factors in estimating the charge to depreciation. The weight of this factor in relation to the first two should depend, in all probability, on the amount of work done per year. If the tractor is used but little, it becomes worthless owing to depreciation independent of use, and to obsolescence, long before it has accomplished the work of which it would be capable if operation 11

Smith and Jones, op. cit., p. 12. Schwantes and Pond, op cit., p. 30. "Farm Organization as Affected by Mechanization, p. 92. 14 See, however, pp. 25-27 of that study, where probably another principle is involved. 11

METHODS OF C O M P U T I N G COST 67 were the decisive factor. Contrariwise, if the tractor is used much, it is worn out in a few years. The time element in this case is so small that wear independent of operation, and obsolescence, cannot amount to very much. The greater part of depreciation in this case must therefore be ascribed to operation. C H A N G E S I N V A L U E OF SERVICE. From his own experience, everyone knows that the value of the service of a machine decreases as its age increases. Old machines do not run as smoothly as new ones. Breakdowns become more and more frequent. Eventually the dependability of the machine may be so small that the farmer does not believe it wise to bear the risk of using it. At the same time that the service of the machine decreases in value, owing to increasing age, the expenses for fuel, lubricants, care, and repairs increase. It is assumed that the value of the service of machines, or their efficiency, at first declines slowly, while in the latter years of their life this decline proceeds at a faster rate.15 Age in this connection evidently covers all three factors discussed above as affecting duration of life. It includes first of all wear independent of use. If an unused machine is affected by weather conditions to such an extent that eventually it has only scrap value, the value of the service of the machine in the interim also must be affected. Obsolescence affects the value of the service the more strongly the greater the improvement undergone by the type of machine; and whereas the older machines provide less service and involve higher direct costs than when they were new, the most recent models are more efficient than the old ones were at comparable ages. Actually, the quality of the service usually is affected most by the amount of operation. The investigators who use the straight-line method of computing depreciation have to put their trust in the assumption that the variations in the age of the machines to be depreciated "Presented graphically, the efficiency curve is concave to the point of origin. See Saliers, Depreciation, Principles and Applications, p. 63. Saliers' curve approximates a very slowly declining straight line for more than three-fourths of its length and then falls sharply. But efficiency as demonstrated b y Saliers seemingly is merely ability t o perform a certain function, without consideration of whether the cost of maintaining it shows substantial increases during the life of the machine. T h e curvature of a curve representing efficiency including maintenance and operating expenses would be much less than that of Saliers' curve.

68 METHODS OF COMPUTING COST will be taken care of by the method of averaging. In other words, they assume that the averages of the halved lifetimes of the different machines weighted by their prices (this is the average which is used in the method) will be about equal to the averages of the actual ages, also weighted by prices (this is the average which should be used). If a great number of different machines, or a small number but with a not very large difference in price, is used on a farm, it may frequently happen that the above expectation will materialize, and that the weighted average of the actual ages of all the machines will remain close to the weighted average of their halved lifetimes from one year to another, because the increase in the age of some machines is offset by the replacement of other machines by new ones. Thus by taking the average of the halved lifetimes, i.e., by disregarding the actual variations in age, no great harm is done, except when many new or financially weak farms are included.19 Disregarding the actual variations in age is more likely to have harmful consequences for farms using such expensive machines as tractors or combines; if such a machine is new (or old), it can considerably reduce (or increase) the weighted average of the actual age of the whole set of machinery. Moreover, the part played by tractors on farms is so important that a new set of machines drawn by an old tractor is likely to do appreciably less work than a set of machines of average age with a new tractor. It is even more risky to disregard variations in actual age when the operating costs of individual machines have to be computed. As regards tractors, there is one more important reason which makes an equal yearly rate of depreciation inappropriate. Old tractors are, on the average, used fewer hours per year than new ones. Farmers with old tractors are likely to keep more horses than comparable farmers with new tractors. Likewise, a farmer who relies on one tractor as the main source of power frequently is not satisfied with a nearly worn-out tractor. Rather he will prefer to buy a new tractor, retaining the old one for peak work, emergencies, and so forth, or selling it. Schwantes and Pond, who conducted their study in 1928, have " T h e last exception may become the rule under conditions such as those which prevailed during the late depression.

METHODS OF COMPUTING COST 69 shown that in Minnesota tractors bought after 1924 have been used, on an average, about SO days per year, while the annual use of tractors bought in 1923 and earlier amounted to only about 40 days.17 When a yearly rate of depreciation, proporCHART 3 YEARLY DEPRECIATION CHARGE OF TRACTORS OF DIFFERENT AGE, DETERMINED BY APPLICATION OF T H E INVENTORY METHOD Based on 172 tractors on New York farms, 1926. Data from Gilbert, An Economic Study oj Tractors on New York Farms PERCENT

Percent

of first cost J

^

Percent

6-7

4-5

of present

value

2-3

t-2

25

20 15

10 5

0

8-9

7-8

5 6

3-4

0-1

YEARS OLO

The yearly depreciation charge was determined by asking the farmers to state the value of their tractors at the beginning and at the end of the year. The difference between the two is expressed in percent of the first cost and of the present value of the tractors. The yearly depreciation charge, computed by the application of the inventory method, clearly reflects the reduced value of the service of the tractors during the later years of their life, which is disregarded when the much-used straight-line method is applied. The inventory method probably even overemphasizes the above fact.

donate to the estimated life, is applied to tractors the annual utilization of which has been greater before than in the year of investigation, and which probably will be used still less in the future, this procedure is equivalent to using a higher de" T h e fact that machines used but little last longer than machines used intensively must have had some part in this result. It seems unlikely that it accounts for the whole difference, however.

c

tî .2 23o-2?8, " (^HNfJN o » » .S G o cm3o i: _ . . o> r-i • ü— £.5 S " Q .S —>

o M Ss tí H H H Q ¡zf O hH-( < — iUi w tí euu Q QS O Ho 2 HH Ef OS ¿ tí S > < < X tí u o uH 55 s H > 5>: S o t/2 « M g O H O >< < « tí h

h O H C < S h O H O H tu l* H

s:Joi^"aS2

OoC^O'^NN'û'O

« I.S §.s - s « Oh 3>-a

0N0»0«N«0

TC3 rt 1e

ic

•O £

« ¡2 8: § ¡a io M «M W5 o «O N H. ^O fSrjfSfOf^'OOvfSO 2E "o "O -«(

I

U3) « (S) S se ^ ^ TH^^CSCSfO'tlO'O 4 Ì ft Soe§ n o t S « a -C c s

1

•

H IO N ON O O* -hi ioœ toct»^O to V) I e

«

c £3 eo .S rt s U

OOOvO-'NfO^'i^'O1 ^^ Qv ^ O

O

METHODS OF C O M P U T I N G COST 71 preciation charge per hour of work in later years, as compared with that in the first years of the same tractor. 18 Survey data show that farmers realize that the value of the service of their tractors is different at different ages of the tractor. When farmers are asked about the value of their tractors at the beginning and at the end of the year of the survey, their answers usually indicate that the annual decline in value progresses rapidly as the age of the tractors increases. This is shown by the data collected by Gilbert on New York farms, and reproduced here in Table 4 and in Chart 3. We assume, therefore, that the depreciation charge should decline as the age of the tractor increases, parallel to the declining service rendered by tractors. Methods used and recommended.—It is hardly necessary to say that the straight-line method, usually employed in tractor studies, does not meet the requirements elaborated above. The main obstacle is that this method completely disregards the decreasing value of the service of the older tractors. The reducing-balance method described, for instance, by Saliers, in his Depreciation, Principles and Applications,19 is not used in tractor studies and is mentioned here merely as a contrast to the usual procedure. The charge to depreciation on the basis of the reducing-balance method is computed by applying the same percentage to the balance of the value (remaining value) that the commodity to be depreciated has at the beginning of each accounting year. For instance, for depreciating a machine in 25 years, 16.82 percent of the balance of the value of the machine at the beginning of each year shall be applied. Chart 4 shows that the rate of depreciation provided by this method is very high in the early years and negligible in the later years. In the above example of a machine to be depreciated in 25 years, the rate of depreciation is 14.00 percent in the second year and only 0.24 percent in the last year but one. Presented graphically, the charges computed according to the reducing-balance method yield a curve which is strongly convex to the point of origin (see Chart 4). Considerable deviation of * This is what happened with the tractors included in the Missouri study. The two-year-old tractors bore a lower per-hour depreciation charge than the obsolete models averaging 8.3 years (see p. 12 of that study). " Pages 144-50.

72 METHODS OF COMPUTING COST the curve representing the rates of depreciation from the concave efficiency curve (see footnote 15 to this chapter) may be justified, if a formula is desired for use by the individual entrepreneur. He may find it good practice to insure himself against all possible risks by accumulating in the early years of the service of the machine more funds than would be necessary under normal conditions. Thus rates of depreciation in different years having the form of a straight line or of a convex curve may serve his purpose better than rates forming a concave curve. But the rate of the decline in the charge to depreciation provided by the reducing-balance method seems to be excessive even for this purpose. While a machine may show a profit, if a reasonable charge to depreciation is made, a loss might be indicated for it in the early years of its service if the depreciation were computed according to the reducing-balance method. The "sum-of-year-digits" method is similar to the reducingbalance method in that the charge to depreciation is large in the first years and small in the later years of the life of the tractor. But while the rates computed by the reducing-balance method yield a convex curve, the sum-of-year-digits method provides for a decline of the charge to depreciation in a straight line (see Chart 4). The sum-of-year-digits method is as follows: The number of years comprising the life of the machine is summated; in the case of a commodity to be depreciated for 20 years we shall have 1 + 2 + 3 18 + 19 + 20 = 210. The next step is to divide 100 by the sum-of-year-digits, in this case 210. The quotient multiplied by 20 minus the age of the tractor at the beginning of each year provides the rate of depreciation for the respective year. If, for example, the total life is 20 years, the rate of depreciation in the third year 100 X 18 will be equal to = 8.57 percent of the first cost; 210

in the last year it will be only

100

= 0.48 percent.

210

An evaluation of the commodity at the end of each year, necessary for applying the inventory method referred to above, may be made on the basis of either the market value or the use value of the tractor. There is no reason to assume that the market value is a true reflection of the use value. Since it will

METHODS OF COMPUTING COST 73 not be easy for farmers to ascertain the use value, they probably will tend to give the market value. This seemingly was the case with the farmers questioned by Gilbert (p. 71 and Chart 3). Since farmers buy tractors for use on their farms and not for sale, a method of calculating depreciation which involves the risk that the use value will be replaced by the market value can hardly be regarded as an appropriate substitute for the usual procedure. Also, the depreciation computed by the inventory method may be easily affected by a change in the price of tractors, if such a change occurs during the year of observation. Such an increase in price may perhaps explain the small charge to depreciation of general-purpose tractors in Champaign and Piatt Counties, Illinois, in the 1935 accounts.20 The average charge to depreciation in that year was only $49.97, as against $71.14 in 1934, and $78.06 in 1933. As a result, the cost of tractor power per hour went down in 1935, according to the accounts, although an increase might have been expected. A method providing for, or permitting, depreciation or appreciation for changes in the price of tractors during the year of investigation may be correct for certain purposes, but it is inadequate for comparisons of the cost of different types of power.21 In his "Comments on Depreciation and Repairs of Combine Harvesters and Tractors on the Canadian Prairies," Grest undertook to meet the requirements of an adequate rate of depreciation in a more elaborate way than those described above. The depreciation charge proposed by Grest consists of two parts. The first part is intended to cover depreciation on obsolescence and is therefore independent of operation. It is a yearly charge, computed by the application of the sum-of-yeardigits method, under the assumption that an unused tractor, after twenty years, has only scrap value. To the yearly charge an additional charge (0.042 percent of first cost) for each hour of operation is added. Thus the more the tractor is used, the more is its life reduced from the twenty years assumed for an unused tractor. x 1035 Complete Cost and Farm Business Analysis on 39 Farms in Champaign and Piatt Counties, Illinois, pp. 51-53. 11 If the inventory method is used for the computation of the depreciation charge of horses, the effect of changes in horse prices has also to be eliminated in order to make the comparisons significant.

74

METHODS OF COMPUTING COST Grest's proposal meets almost all major requirements of a properly devised rate of depreciation. Since the charge to operation remains unchanged during the whole life of the tractor, the extremity of the decline in the rate of depreciation with the increase in the age of tractor, inherent in the sum-of-year-digits method, is considerably toned down. A disadvantage results from the fact that the ultimate charge is composed of a rapidly declining yearly sum and a stable per-hour charge. For the decline of the ultimate charge (the ratio between the rate of depreciation in the last year of service to that in the first year) thus becomes dependent on the proportion which each of the two primary charges assumes in the ultimate charge. And this proportion, in its turn, depends on the amount the tractor is being used per year. For example, for tractors used 200 hours per year, the rate of depreciation in the last year is 40.5 percent of that in the first year; for tractors used 1,000 hours per year, the percentage is 72.6. Furthermore, it is hardly commendable to make obsolescence the basic factor in computing the charge for depreciation of tractors with a high annual use. Apart from this, the increase in the total work of tractors during their life, which accompanies the increase in the annual use of tractors, is probably excessive, when Grest's formula is used (see Appendix II, part B). Method suggested.—The charge, computed according to the method recommended by the present writer, also consists of two parts: one is intended to cover charges not dependent, the other those dependent, on operation. As in Grest's proposal, the first of the charges is a yearly one, while the second is computed on a per-hour basis. But the ratio between the depreciation charge in the first and in the last year of service is independent of the number of hours that the tractor is used during the year. Other important advantages also may be claimed for the proposed method. The rates for the depreciation charges, computed in accordance with this method, are as follows: Charge on wear independent of work, and on obsolescence: 7.S percent per annum applied to an average between the first cost and the remaining value of the tractors. Depreciation on operation: 5.34 percent per annum applied to an average between the first cost and the remaining value, divided by the number of hours that the

METHODS OF COMPUTING COST 75 tractor can be used annually during a working life of ten years, per hour of operation. (Remaining value is the part of first cost not depreciated at the beginning of each accounting year. Value remaining at the end of the last year of the use of the tractor [scrap value] is assumed to be equivalent to 3 percent of first cost.) In Appendices II and I I I are presented detailed computations of the working life, of the total work during useful life, of the proportions of fixed charges to total charges, and of remaining values after 5 and 10 years of service, at different amounts of annual use, arrived at by the use of the proposed method, for tractors which can perform different amounts of annual work during an assumed working life of ten years (a range from 486 to 1,068 hours per year is covered).22 Computations of the annual depreciation rates for Tractor B, not used, used 200 hours per year, and used 500 hours per year, also are shown. Grest's computations, the findings of the Missouri study,28 as well as data for the straight-line and the reducing-balance methods are likewise presented, for purposes of comparison. The main feature of the writer's proposed method is that both the fixed and variable charges are constant percentages, applied to a combination between the first cost and the remaining value. The utilization of both the first cost and the remaining value as a basis for computing the rate of depreciation is new, so far as the present writer is aware. It is intended to obviate the rigidity of the usual methods, which give the investigator only a choice between using a charge computed by applying a constant percentage to the first cost and therefore remaining equal during the whole life of the machine (straight-line method); or else employing a charge which is derived by applying a constant percentage to the remaining value and which may therefore be too large in the first years of service and too small in the final years. By combining the first cost and the remaining value, a basis lying between them may always be found, which —with a constant percentage applied to it—-will fit the requirements. More specifically, we shall have a more or less steeply " The designation of the charge on wear independent of use, and on obsolescence, is abbreviated in the tables, as well as later in the text, to "fixed charge"; and that of the charge on operation to "variable charge." " Smith and Jones, op. cit.

24

1

2

3

4

5

6

7

8

9

10

It

12

9

10

13

14

15

16

17

16

32

I

2

3

4

5

6

TRACTO'RS I 24

16

I

7

USED 500

8

HOURS

II

PER YEAR

12

13

14

CHART 4 YEARLY DEPRECIATION CHARGE OF TRACTORS, EXPRESSED I N P E R C E N T OF FIRST COST, AS COMPUTED BY D I F F E R E N T METHODS Data are from Appendix II, part C. The rates according to the recommended method are for a tractor with a total work of 5,340 hours during a working life of ten years (Tractor B). Scrap value is assumed at 3 percent of first cost, except for Grest's method, where 3.7 percent is allotted for this purpose. The curve for the recommended method in part A of the graph should be extended over another 0.36 year. In part B of the graph, the tractor is depreciated in 13.64 years according to Grest's method, and in 13.47 years according to the proposed method. The curves in part C should be extended over another 0.59 years (Grest's method) and 0.28 years (proposed method). The straight-line method, usually employed in power studies, provides equal rates of depreciation from the first to the last year of a tractor's life, in spite of the reduced value of its service and increased cost of fuel, lubricants, repairs, and so forth, in later years. The application of the reducing-balance method, not used in power studies, results in very high rates of depreciation in the early years of the life of tractors, and in practically negligible rates in the final years. The rate of depreciation computed by the sum-of-year-digits method likewise decreases to nearly naught in the last year (see Part A of this chart). Combined by Grest with a rate of depreciation which does not vary during the life of the tractor, the depreciation charge computed by the sum-of-year-digits method decreases more slowly, but the rate of the decline is different for tractors with different amounts of annual use. When the writer's recommended method is applied, the depreciation charge declines at about the same rate for tractors with different amounts of annual use. In the last year of service, it is somewhat greater than half of the rate of the first year, for all tractors.

78 METHODS OF COMPUTING COST declining series of averages between first cost and remaining value. A constant percentage applied to them yields a series of similarly declining absolute charges to depreciation. An unweighted average between the first cost and the remaining value has been used by the writer as the basis for computing the total as well as the fixed and variable charges. The result is that the charge for depreciation becomes in the last year of service about half of that in the first year, with intermediate years nearly pro rata. The assumption of such a decline of the rate of depreciation is, of course, arbitrary. Combined with the other charges against the work of the tractor, however, this rate seems to provide total costs of tractor power which in many cases reflect fairly well the lesser value of the work of older tractors as compared to that of new ones. When the difference between the cost of the work of new and old tractors, derived by using as a basis the unweighted average between the first cost and the remaining value, is found to be either excessive or too small, the necessary adjustment can easily be made by changing the ratio between the first cost and the remaining value. By giving the first cost twice the weight of that of the remaining value, in computing the average, a scale of depreciation rates is arrived at in which the charge to the work of the tractor in the last year is about two-thirds of that in the first year. Conversely, to get a charge which in the last year of service is about one-third of that in the first, the remaining value should be given twice the weight attached to the first cost. The curves in Chart 4, representing the charges according to the proposed method, are convex to the point of origin. But the curvature is almost negligible, if an unweighted average between the first cost and the remaining value is used as the basis. This would indicate a defect in the proposed method, if the curve of the efficiency of tractors (efficiency that considers the differences in both the maintenance and the operating costs, were found to be strongly concave. For the accumulation of large reserves in the first years of the service of the machine may be good practice for a private entrepreneur but is contrary to the interests of a student looking for comparability of the data on the cost of different types of power. His objective is to find a rate of depreciation that would offset the reduced value of the service of the tractor, and this apparently calls for rates of depreciation

M E T H O D S OF C O M P U T I N G

COST

79

proportionate to the efficiency of the tractor. In order to reach final decisions, much more factual data on the form of the efficiency curve of tractors would be required than are now available. These data would perhaps show that the useful life of tractors commonly terminates before the efficiency curve has started its sharp decline (see footnote 15, p. 67), or at the very beginning of it. In this case the difference between the effective portion of the efficiency curve and the curve representing the charges to depreciation according to the proposed method, which declines in a practically straight line, may prove not so large as to vitiate the latter. Moreover, the appraisal of efficiency includes the consideration of the higher costs of repairs in the later years of the service of the tractor. This study suggests, however, using equal charges for repairs in all years of the life of the tractor (see pp. 102-14). Hence the curve representing the rates of depreciation can show some deviation from the efficiency curve. In particular, it does not need to go down to almost naught so long as the tractor still is usable for farm work. TOTAL ANNUAL RATE. L e t us, however, explain in greater de-

tail how we derive our rates. There is no means for determining the fixed and the variable rates separately. Rather the procedure starts by computing the total or combined rate. This rate is derived from the estimated life of a tractor, by the aid of a formula which is closely related to that by which the yearly rate is computed in the reducing-balance method.24 The formula is:

where " x " is the combined rate of depreciation, expressed as a fraction of the average between the first cost and remaining value at the beginning of the year, " n " is the estimated life in years, " V 0 " the first cost, and " V n " the scrap value after " n " years.25 If scrap value is assumed to be 3 percent of first cost, Y'0-f v n as is done by the present writer, the expression — equals 103 — = 0.515. In this case, 200

2V„

x = 2( l - v ' O . S I S ). For example, if V /

"Saliers, Depreciation, Principles and Applications, p. 147. * Derivation of this formula and the one immediately following is given in Appendix I V below.

80

METHODS

OF C O M P U T I N G

COST

the estimated life of a tractor is ten years, x is equal to 2^1 — v ^ . 515^= 0.1284 or 12.84 percent. According to the requirements set forth above, this percentage, when applied to the average between the first cost and the remaining value, will provide a series of declining annual charges which, after expiration of ten years, will leave only 3 percent of the first cost not depreciated. The general formula which permits weights to be attached to the first cost and the remaining value is: 1/

n/(l

—a) V o + a V A

— A ' - y — 7 . — ) ' where " a " is the weight given to the value remaining at the beginning of each year, and (1 — a ) is the weight given to the first cost. The weights are expressed as fractions of their sum. For example, if the first cost is given a weight twice as great as that attached to the remaining value, " a " will be ]/$ and (1 — a ) = 5^.In this case, the expression under the root will be 1100+i-3 / » \ — = 0 . 6 7 6 7 , and x will be 3( 1 - ^ . 6 7 6 7 V If, on 100 \ ) the contrary, the remaining value is given a weight twice as large as that attached to the first cost, " a " will be2/zand (1 — a . ) = y 3 . In this case, x =

1.5

>

— V0.3533

The first of the two formulae should be used if one is satisfied with the unweighted average between the first cost and the remaining value as the basis for computations, but needs a total rate for conditions other than those considered here. One may, for example, consider a working life other than ten years as a more correct starting point, and this would necessitate a new computation. The second formula ought to be applied if a combination between first cost and remaining value other than their unweighted average is considered better adapted as a basis for computing the depreciation charge.26 Whichever formula is used, first the total work possible during a certain number of years, or the duration of life of a " T h e formulae, of course, can also be used for computing the life of the tractor if the total annual charge for depreciation is known.

METHODS OF COMPUTING COST 81 tractor used for a certain number of hours per year, has to be estimated. 27 Estimating the yearly work of a tractor with a life of ten years seems to produce satisfactory results. In making estimates, the year or years of construction of tractors, i.e., the degree of their perfection, has, of course, to be assumed to be the same for all types and sizes. If the writer's (or Grest's) proposal be accepted, it will be necessary to include in the questionnaires an inquiry as to the total number of hours which the tractor has been used, preceding the date or year of the survey. This information will also be useful in making many other computations. A farmer who has bought a used tractor will not be able to supply the information about the total work performed to date by that particular tractor. In this case, it would probably be necessary to estimate the work done by the tractor before it was bought by the present owner, from the relation of the price paid for it to the first cost of the same make of tractor in the same year. The figures on the remaining value in Appendix II, part B, may provide some help in making these estimates. S P L I T T I N G T H E TOTAL RATE I N TWO. The total rate now has to be distributed between the rates for the fixed and the variable charges. In making this distribution, it should be remembered that the selected ratio between the fixed and the variable charges to depreciation determines the rate at which the total work of tractors during their life increases or declines as their life is shortened or lengthened. Obviously it was desirable to make the distribution in such a way that the increase in total work be as near as possible to the actual variations, as revealed by the available data. This requirement is so important that the relationship between fixed and variable charges assumed by the present writer must be changed whenever the data indicate a relationship between the total work during the life of tractors and the length of their life other than the relationship assumed by him. A check indicates that fairly good results are attained if from the 12.84 percent accepted as the total rate for depreciation of a tractor with an estimated life of ten years about 7.5 percent is used as the rate for fixed charges, and the remainder " O n l y the life of the tractor needs to be known for the present part of the procedure; but since the life of the tractor is assumed to vary with the amount of yearly work, the estimate has to include both.

82 METHODS OF COMPUTING COST as the yearly rate for variable charges. The selected rate for depreciation caused by wear independent of use, and by obsolescence, is equal for tractors of all types and sizes. Wear independent of use is probably somewhat greater with smaller tractors than with larger ones. Obsolescence also varies for different types of tractors. But different rates would probably mean an avoidable complication. An exception should perhaps be made for very small, light tractors ; a somewhat higher fixed charge may be adequate for them. A fixed rate of 7.5 percent per annum, applied to the average between the first cost and the remaining value, will depreciate an unused tractor in 17.36 years. As unused tractors are a fiction, we do not consider this part of the formula, taken separately, significant.28 Since the total charge is the same for all tractors with an equal length of life, independent of the amount of work performed during their life, and since the rate for the fixed charge also is assumed to be the same for all tractors, the hourly rate for the variable charge has to decline as the number of working hours during the same length of life increases. For the same yearly rate for the variable charge is distributed among the greater number of hours that stronger tractors, during a life of the same length, are able to work. The variable rates for tractors of different durability, for which computations of the length of life, total work during life, and so on have been made in Appendices I I and III, and the corresponding total work during a life of ten years, are as follows: _ Tractor

T, ... „ , Vartable Rate . „ Per Hour

Total Work T ! , 1^en Lt e 0

During

T/

Years

in Hours

A .011 4,855 B .010 5,340 C .009 5,933 D .008 6,675 E .007 7,629 F .006 8,900 G .005 10,680 A combination of the fixed and the variable rates of Tractor " The second part of the formula, providing for depreciation on operation, is likewise not intended to be used alone, since nobody will run a tractor uninterruptedly. Both parts of the formula are so adjusted that, if used in conjunction, a fairly reasonable result is secured.

METHODS OF C O M P U T I N G COST 83 A yields figures for the number of hours of annual use at different lengths of working life, or vice versa, which are similar to those computed in the Missouri study (see Appendix II, part A).2* The only difference, and that of no great significance, is that Tractor A will take a little more time to depreciate, if used a small number of hours per year, than would be the case according to the Missouri data. The figures on the length of life for Tractor B coincide with those computed by Grest, when the annual use is small, but they decline more rapidly as the annual use increases. This is considered one of the advantages of the recommended method. While, according to the latter, Tractor B, when used 1,200 hours per year, can last 6.47 years and can perform a total of 7,764 hours' work during its life, Grest's figures for the same amount of annual use are 7.6 years and 9,085 hours respectively. The fixed and the variable rates selected for tractors with a working life equivalent to ten years show a relation between the fixed and the variable charges of 7.S to 5.34, i.e., the fixed charge is equivalent to 58.4 percent of the total charge. When the tractor with a certain number of annual hours of work, during a working life of ten years, is used less intensively, its working life is extended and the proportion of the fixed charge is increased, and vice versa. For instance, it may be observed from the data in Appendix III, part A, that for Tractor B, which is supposed to last ten years if used 534 hours per year, the depreciation independent of operation comprises 78.9 percent of the total depreciation charge, when this tractor is used 200 hours per year, while the fixed charge is 38.5 percent of the total charge if the same tractor is operated 1,200 hours per year. These variations in the proportion of fixed and variable charges to the total are entirely in line with the facts. When the tractor is used little, it is depreciated primarily by wear independent of use and by obsolescence, rather than by operation. On the other hand, intensively used tractors are depreciated primarily by operation.30 " S m i t h and Jones, op. cit., p. 12. " T h e present writer's earlier study was made in Germany, where the f e w operated tractors are used intensively throughout the year. This may be mentioned in explanation of the fact that the total charge for depreciation proposed in that study was made dependent primarily on operation. It is hoped that in the arrangement suggested above each of the various factors determining depreciation receives the valuation it deserves.

84

METHODS OF COMPUTING COST Since the same rate is applied for computing the fixed charge for tractors doing different amounts of work during the same length of life, while the hourly rate for the variable charge declines as the estimated life of tractors used the same number of hours per year increases, the proportion of the fixed charge to the variable charge is different for tractors with a different estimated life, when the number of hours they are used per year is equal. As shown in Appendix III, part A, the ratio between the fixed and the variable charges is as 57.7 to 42.3 for Tractor A, when it is used 500 hours per year. For Tractor G the same relation, at the same amount of annual use, is as 75 to 25. These variations in the proportion of fixed and variable charges again are in agreement with the facts. Stronger tractors can do more work during a life of the same length. Hence the proportion of variable charges is less for them than for less powerful tractors when they are used the same number of hours per year. It may be useful to mention that the final selection of the rates has been made so as to get round numbers for the yearly rate for the fixed charge and for the hourly rate for the variable charge. Seven and a half percent is practically a round number, and the figures which remain for the variable charge (0.011, 0.010, 0.009 percent and so on) after using 7.5 percent as the fixed charge, are even more so. Moreover, the same tractor which can be used 534 hours per year for ten years will be fit to work 500 hours per year for 10.28 years, according to our assumptions. The yearly rates for fixed and variable charges in this case are 7.5 and 5 respectively, and the relation between them is that of 60 to 40. This relationship we had in mind when selecting the rates. Thus a total fixed charge of 12.5 percent and a relation between the fixed and the variable charge of

»

¡a

3 CL O " V >o c „ (4

5 o u ¡£ S J S Ï "3 o1 n ^r «5

oo »o M M es M

r^l^NO

BASIS FOR COMPARISONS OF COSTS 157 Belt will tend to have a smaller proportion of land in cotton than will horse farms. The Georgia investigation affirms this assumption in a striking manner. As shown in Table 13, in two of the three investigated areas the percentage of total crops in cotton was appreciably smaller on tractor farms than on horse farms. In the third area it was practically the same on both tractor and horse farms. Tractor farms of all size groups had proportionately 23 percent less acres in cotton than horse farms.7 The authors of the study comment on these figures as follows:8 [The addition of a tractor] usually caused a change in the cropping system. Reduction in cotton acreage and increase of acreage in feed crops and winter legumes usually occurred. Since the power requirements of cotton are large, a smaller proportion in cotton may be accompanied by a lesser average amount of power used per crop acre on the respective farms. Hence a comparison of the cost of power per crop acre will favor tractors. In order to secure their own power for at least part of the belt work, farmers who need considerable amounts of silage are more likely to keep tractors than farmers who husk their corn from standing stock by hand, or hog it down. Moreover, the tractor might have been bought for considerations other than the amount of belt work. Yet after the tractor is purchased and a cheap source of belt power has become available, farmers frequently find it expedient to make such changes in farm organization as will enable them to take more advantage of this. Somewhat more belt work, however, is done on tractor farms than on horse farms even if the farm organization remains unchanged (grinding of feed, for example). Rolling country makes the use of tractors less profitable and increases the amount of power needed per acre. When studies are made in regions with uneven surface, it must be expected that the tractor farms surveyed, on an average, will be more level than the surveyed horse farms. Hence conclusions as to the superiority of different sources of power, drawn from com1 The proportion of the total crop acreage devoted to cotton was highest also on the investigated Delta plantations that did not use tractors. Reynoldson et al., Utilization and Cost of Power on Mississippi and Arkansas Delta Plantations, p. 3. 'Fain et al., op. cit., p. 54.

158 BASIS FOR COMPARISONS OF COSTS parisons of costs of power per crop acre, are likely to be biased against horses. It can be taken for granted that the number of trucks on farms rises with the increase of the average distance from the railway station. 9 Dairy farmers, who keep relatively more trucks than other farmers of comparable size in the same regions, have also more hauling per crop acre than the other farmers. A farmer who wishes to deliver his livestock to a central market is also more likely to keep a truck than a farmer who sells to local dealers. Last but not least, whoever already owns a truck tries to make as much use of it as he can. Considerably more trucks, however, are kept on tractor farms than on horse farms. 10 Thus it becomes probable that in many areas much more hauling is being done on tractor farms than on horse farms. Variations in the amount of power work per crop acre are likely to impair not only comparisons of the cost of power on tractor and horse farms, but similar comparisons for farms with different tractors as well. An important cause is the possibility of using the general-purpose tractor for cultivating row crops. This possibility may have induced some farmers with general-purpose tractors to plant proportionately more row crops than similar farmers with ordinary tractors deemed it advisable to do. Consequently the power requirements, computed per crop acre, also may happen to be higher on general-purpose tractor farms than on ordinary tractor farms. COST AND AMOUNT OF POWER PER CROP ACRE ON CORN BELT FARMS

In order to leave no doubt that a comparableness of power costs on tractor and horse farms, computed per crop acre, cannot be attained by increasing the sample, a more detailed analy' Tolley and Church, for example, wrote in Motor Trucks on Corn Belt Farms (p. 2 ) : "Another striking point concerning the farms on which trucks are owned is their great distance from the market as compared with other farms in the same section." 10 One of the reasons is that tractors of most types cannot be used for hauling, and rubber-tired tractors, although adapted to haulage, are very little used for this purpose on farms. Hence the use of tractors for drawbar and belt work provides a stimulus for using trucks for hauling. Conversely, where trucks are used for hauling, there is an additional inducement to use tractors for the other work. The elaboration of this problem is given by the writer in Der Schlepper in der Landwirtschaft.

BASIS FOR COMPARISONS OF COSTS 159 sis of the data presented in the study, Utilization and Cost of Power on Corn Belt Farms, is expedient. The number of farms included in the study is higher than that of any other power study except the Illinois study. The Illinois study, however, is based not on survey data, but on accounting data, from which no computation of the amount of work done per crop acre can be made. So far as survey data are concerned, no other study can boast as many farms as the Corn Belt study. Once it is clearly shown that even the data on the cost of power per crop acre on farms with different types of power, collected by that study, are not strictly comparable, owing to variations in the amount of power work per crop acre, probably no further proof need be adduced that the crop acre cannot serve as a reliable basis for comparing the cost of power on tractor and on horse farms. Analysis of the data of the Corn Belt study will also reveal the relation between the cost and the amount of power work per crop acre separately, in each of the three principal kinds of power work: drawbar work, belt work, and hauling. Figures on the cost of drawbar work are found in Table 20 of the Corn Belt study. The cost of belt work was computed by the present writer by adding the cost of tractor belt, miscellaneous power (owned and hired), and hired steam-engine work, from Tables 16 and 18 of the study. The difference between the total costs and the costs of drawbar and belt work was assumed to represent the cost of hauling (Chart ll). 1 1 Hauling—According to the computations of the authors of the Corn Belt study,12 there was a very large variation in the amount of hauling between farms with and those without their own trucks. Road hauling with horses and trucks amounted to 1,059 miles on farms owning trucks, and to only 189 miles on farms with the same crop acreage but without trucks. 13 The higher expenses of the latter farms for hired hauling ($53.41 as against $39.58 on farms with trucks) could make up only for a small part of this difference. Now, on each 100 general-purpose 11 Miscellaneous sources of power are not used exclusively for belt work. Our assumption, however, does not change the results to any noticeable extent, as even the total work of the miscellaneous sources of power constitutes only a negligible part of the total work. a Reynoldson et al., Utilization and Cost oj Power on Corn Belt Farms, p. 12. "See, however, p. 175 as to the compatibleness of the mile and the ton-mile, covered by trucks and by horses.

160 BASIS FOR COMPARISONS OF COSTS tractor farms, there were 31.8 trucks, and on each 100 ordinary tractor farms, there were 27.1 trucks, while there were only 8.5 trucks to each 100 horse farms.14 Hence it must be assumed that CHART 11 COST OF POWER PER CROP ACRE FOR D I F F E R E N T KINDS OF WORK ON HORSE AND TRACTOR-AND-HORSE FARMS IN T H E CORN BELT, 1929

100139

1 - Two-plow 2 - Three-plow

140179

1802202603 0 0 AND 219 259 299 OVER SIZE GROUP OF FARMS (CROP ACRES)

tractor /arms tractor farms 5 = Big-team

5 = General-purpose 4 - Ordinary horse hitch farms

tractor farms

OVER 100 AVERAGE

farms

Data from Reynoldson et ol., Utilization and Cost of Power on Corn Belt Farms. Drawbar work is the only kind of farm power work for which both tractors and horses are used. There is no competition between tractors and horses in belt work and, except for some rubber-tired tractors, in hauling. Moreover, amounts and costs of belt work, and particularly of hauling, show great variations between different type-of-power farms. Therefore, data on the cost of drawbar power per crop acre should be used, in preference to those on the cost of all power, as a basis for conclusions on the competitive position of tractors and horses as sources of farm power.

much more hauling, on an average, was done on tractor farms than on horse farms. If we now turn our attention to Chart 11, we will not be sur" The horse farms cited here and in other parts of this work from the Com Belt study refer to the ordinary horse farms of that study. The big-team-hitch farms of the Corn Belt study are always cited in full.

BASIS FOR COMPARISONS OF COSTS 161 prised to see that, although the cost of hauling per mile on horse farms is likely to have been higher than on tractor farms, tractor farms of all size groups—with only one exception out of 18 cases —spent more for hauling than horse farms of corresponding size. The large differences in the cost of hauling on farms with different types of tractors also are significant. The SO horse farms, with 140 to 179 crop acres each, spent for hauling, on an average, 68 cents per crop acre, while the 17 three-plow tractor farms spent $2.22, i.e., more than three times as much. The 31 two-plow tractor farms and the 18 general-purpose tractor farms of the same size group occupied an intermediate position, with $1.29 and $1.27 respectively spent for hauling per crop acre. The greater amount of hauling per crop acre on tractor farms, as compared with that on horse farms, renders data on the cost of power per crop acre, when these include the cost of hauling, unusable for ascertaining the profit, if any, from the use of tractors. Moreover, since tractors have no direct bearing on hauling, the same situation is created by the mere fact that the cost of hauling per crop acre on tractor farms is different from that on horse farms (without regard to the amount of hauling). This is true, of course, only where the cost of hauling is not affected indirectly by the type of power used for drawbar work. Belt work.—The amount of hauling depends on many circumstances which have little or nothing to do with crop or other kinds of acreage. Variations in the distance from market, in the number and in the kind of livestock, and in marketing methods are the principal factors affecting haulage. Greater similarity between tractor and horse farms might be expected as to the amount of belt work per crop acre, since this primarily consists of threshing the products grown on the crop acreage. But different crops require different amounts of belt work, some requiring none at all. The data of the Corn Belt study indicate that the variations in belt work are, in fact, very significant. According to Table 4 of the Corn Belt study, tractor farms, on an average, used 0.29 hours of belt power (tractor, steamengine, and miscellaneous sources of power) 15 per crop acre, as "The time each of these machines was used had to be added without any weighting, since aside from the owned tractors no data are available as to the size of the machines.

162 BASIS FOR C O M P A R I S O N S OF COSTS against 0.14 hours on ordinary horse farms. Although the horse farms had to pay for hired tractor work many times as much as the belt work of owned tractors cost the tractor farmers, horse farms spent for belt work only 66 cents per crop acre, as against 73 cents spent on ordinary two-plow tractor farms, 70 cents spent on ordinary three-plow tractor farms, and 71 cents spent on general-purpose tractor farms (Chart 11). Thus seemingly not very divergent figures on the cost of belt work conceal large variations in the amount of that type of work. The variations in the amount of belt work, like those in the amount of haulage, were particularly large on small farms. In the size group with 100 to 139 acres in crops, the belt work amounted to 0.39, 0.36 and 0.25 hours per crop acre on twoplow tractor, three-plow tractor, and general-purpose tractor farms respectively, while the figure for ordinary horse farms was only 0.14 hours. On farms with less than 100 acres in crops, the variations were still larger. Owing to the larger amount of belt work per crop acre on tractor farms as compared with that on horse farms, data on the cost of all power per crop acre, i.e., data on the cost per crop acre, including the cost of belt work, are inappropriate for conclusions on the superiority of tractor or horses as the source of farm power. Drawbar power for growing and harvesting crops.—According to the Corn Belt study, Corn Belt farms operating tractors are doing more hauling per crop acre than horse farms. We know further that they also are doing much more belt work per crop acre. It is not impossible, therefore, that, by eliminating both items from the cost of all power, the comparableness of the residual figures would be considerably increased, even if no further adjustments were made. In this case, the data on the cost of drawbar work per crop acre could be used for the comparisons of different types of power, in preference to the cost of all power. This comparison may even be considered particularly significant, since drawbar work for growing and harvesting is the only part of farm work in which both tractor and horses compete directly. A comparison of the figures on the cost of all power and the cost of drawbar power only in Chart 11 shows that the above expectations are not without foundation. Disre-

BASIS FOR COMPARISONS OF COSTS 163 garding discrepancies, which in part probably result from the smallness of the sample, we find that the figures on the cost of drawbar work reveal more reasonable relationships than do the figures on the cost of all power. The reason why dealing with the cost of drawbar power, instead of the cost of all power, improves the results is, that by taking a sufficient sample, differences in the amount of drawbar work per crop acre between tractor and horse farms are eliminated to a greater extent than are differences in the amount of hauling and belt work.16 Still, lessening the differences is not equivalent to eliminating them. And only the absence of any differences would permit the use of the data on the cost of drawbar power on various type-of-power groups of farms for conclusions on the superiority of one of the sources of power. In order to ascertain whether the differences in the amount of work between the various type-of-power groups included in the Corn Belt study are entirely eliminated by excluding from the cost of all power per crop acre the cost of hauling and belt work, a computation of the amount of drawbar work on those farms has been attempted by the writer. The computation was made by converting the work of all sources of power into horse-hour equivalents. Of necessity, this could be done only very roughly. For instance, the horse-hour equivalents used were not computed, but estimated on the basis of the original data. Only a single equivalent in horse hours for each type of tractor was used, although horse-hour equivalents vary to some extent with variations in the size of farms and in the character of the work done by tractors.17 By dividing the total cost of drawbar power " It is significant that differences in the amount of drawbar work are smaller than those in the amount of belt work and hauling, although the variations in the requirements of individual crops for drawbar work are as large as are the variations in their requirements for belt work and hauling. This divergence indicates that in the Corn Belt the organization of farms buying tractors differs from the organization cf horse farms less as to the crop sequence than as to the methods of marketing the farm products, or that the use of tractors affects the crop sequence less than it affects the method of harvesting and marketing the products, or that both of these groups of conditions are effective simultaneously. A similar situation probably is encountered in many other regions. " The procedure employed was as follows. B y multiplying the cost of drawbar work per crop acre, giver, in Table 20 of the Corn Belt study, by the average number of crop acres per farm in each farm group, the total cost of drawbar work per farm was computed. From these figures the cost of tractor drawbar

PERCENT 2-PLOW

TRACTOR

GENERAL-PURPOSE

FARMS

TRACTOR

FARMS

SIZE OF FARM (CROP ACRES)

Per crop acre

E3

Per horse-hour

equivalent

C H A R T 12 T H E E F F E C T ON T H E C O M P A R A T I V E COST O F DRAWBAR P O W E R OF E L I M I N A T I N G T H E D I F F E R E N C E S I N T H E A M O U N T S O F DRAWBAR P O W E R U S E D P E R C R O P ACRE, C O R N B E L T , 1929 The graph shows the percent by which the costs on tractor-and-horse farms are higher ( + ) or lower (—) than on horse farms. The data per crop acre are from Reynoldson et a!., Utilization and Cost of Power on Corn Belt Farms. The data per horse-hour equivalent are computed by the writer. More power work was generally performed per crop acre on the tractorand-horse farms than on the horse farms. After these differences in the amount of power work per crop acre are eliminated by reducing the original data on the cost of power per crop acre to the cost per horse-hour equivalent, the conclusions drawn from the original data are necessarily materially altered.

166 BASIS FOR COMPARISONS OF COSTS per crop acre by the computed number of horse-hour equivalents per crop acre, the cost per horse-hour equivalent was arrived at. In Chart 12 the difference in the costs of drawbar power on tractor and on horse farms, per crop acre and per horse-hour equivalent, is expressed in percent of the cost of this item on horse farms. It will be observed from the data in Chart 12 that the costs of drawbar work per crop acre and per horse-hour equivalent do not coincide. For all groups of farms with tractors, the cost compares more favorably with the cost on horse farms, on the basis of horse-hour equivalents, than it does on the basis of crop acres. The cost of drawbar power on ordinary two-plow tractor farms, which, on the basis of crop acres, was lower than the cost on horse farms by 6.8 percent, when computed per horse-hour equivalent was lower by 9.6 percent. The corresponding figures for general-purpose tractor farms were 13.4 percent and 18.5 percent. Three-plow tractor farms bore a little greater expense for drawbar work per crop acre than did horse farms. The drawbar work done on these farms per crop acre, however, was so much larger than on horse farms that, when computed per horse-hour equivalent, the cost of drawbar work on these farms became lower by 8.9 percent. While four sizegroups of the three-plow tractor farms had higher, and only one group had lower, costs per crop acre than the corresponding groups of horse farms, almost the opposite is revealed when differences in the amount of work are eliminated by reducing the cost per crop acre to the cost per horse-hour equivalent. The changes in the cost of drawbar power which result from computing the cost of power on Corn Belt farms on the basis of the amount of work, rather than per crop acre, are not very work (owned and hired), as given in Tables 16 and 18, has been subtracted. As the residual, the cost of horse work for growing and harvesting was secured. Then the cost of horse work per hour was computed from Tables 16, 18, and 4. By dividing the cost of horse work for growing and harvesting crops by the cost of horse work per hour and by the number of crop acres per farm, the total number of horse hours and the number of horse hours per crop acre spent for growing and harvesting were secured. Finally, the tractor and the horse hours spent per crop acre were added together, after the tractor hours had been reduced to horse hour equivalents by making the rough assumption that a two-plow tractor does, on an average, the work of 8.0 horses, and a threeplow and a general-purpose tractor that of 10.75 and 7.25 horses respectively.

BASIS FOR COMPARISONS OF COSTS 167 large, so far as the absolute size of the changes is concerned. There is no doubt, nevertheless, that these changes are significant and cannot be disregarded.18 If hauling and belt work, which are subject to much greater variations than drawbar work, had not been eliminated, the divergence between the costs computed per crop acre and per horse-hour equivalent would be still greater. Thus evidently a basis more adequate than the crop acre for computations of the cost of power on farms with different types of power is the prerequisite for getting reliable results on the superiority of tractors or horses as the source of farm power. SOME SUGGESTIONS

The shortcomings of the crop acre as the basis for comparing the costs of farm power have been recognized by many investigators. It has become almost a habit to provide data on the cropping system of the investigated farms. These, if carefully studied, are very helpful. The Indiana publications even supplied these data in the tables where figures on the cost of power were presented, thus compelling the readers to take this important factor into consideration. Some studies, however, unfortunately do not include data on the cropping system, or an indication of whether or not the proportion of various crops on farms with different types of power was checked and found equal, or whether the variations in them were so small as not to affect the conclusions. In some cases the data on crops grown, although supplied, are tabulated in a way that does not enable the reader to make the necessary computations. The Minnesota study19 presented the cropping data by investigated regions, disu and In Table 7 of the study, Utilization and Cost of Power on Mississippi Arkansas Delta Plantations (Reynoldson et al., p. 10), t h e mule a n d t h e t r a c t o r drawliar work, used on plantations with different types of tractors, is given in mule-hour equivalents. If the n u m b e r s of mule-hour equivalents per p l a n t a t i o n are divided by the numbers of c r o p acres, it will be seen t h a t o r d i n a r y t r a c t o r plantations used per crop acre 12 percent more m u l e - h o u r equivalents t h a n t h e plantations with general-purpose tractors. Plantations with b o t h o r d i n a r y a n d general-purpose tractors used as much as 20 percent m o r e t h a n t h e latter. It is evident that the effect of such large variations in t h e a m o u n t of power used per crop acre will inevitably conceal any possible effect of the difference in t h e t y p e of tractors on the costs of d r a w b a r power per c r o p acre, particularly if t h e proportion of w o r k done by t r a c t o r s is small, as w a s t h e case on t h e investigated farms. " Schwantes and Pond, op. cit., p. 16.

168 BASIS FOR COMPARISONS OF COSTS regarding size groups, while the figures in Tables 30, 34, 35, and so forth, were by size groups, disregarding regions. Moreover, it is evident that even the fullest data on cropping systems, presented for the use of the readers, are only a substitute for what ought to be done by the investigators themselves. When some crop predominates, the crop acre as the basis of computations is frequently replaced by the acreage in that particular crop; or computations both per crop acre and per acre of the major crop are made. The start in this direction was probably made by the investigators of rice farming.20 In the study, Utilization and Cost of Power on Mississippi and Arkansas Delta Plantations,21 the cost of drawbar power was computed both per crop acre and per acre in cotton. The reason given was: "Since cotton occupied 75 percent of the total crop land for all plantations, the cost of drawbar power per acre of cotton is a more important consideration than the cost per acre of all crops." But comparableness, rather than importance, is the decisive factor in comparisons of the cost of power, and comparableness of the data on the basis of the cost per acre in cotton in this particular case is even less satisfactory than on the basis of crop acres. The cost of power on plantations with both ordinary and general-purpose tractors was higher than on plantations with general-purpose tractors only by 12.7 percent on the basis of crop acres, and by 21.8 percent on the basis of acres in cotton, because the first group had 70 percent and the second group 76 percent of the crop area in cotton. The farms with both ordinary and general-purpose tractors, however, also used greater amounts of power, both per crop acre and per acre in cotton. The computation per acre in cotton increased the negative effect of this fact on the comparableness of the data. The proposal of Smith and Jones, the authors of the Missouri study, appears to be most commendable. These investigators have practically abolished the crop acre and replaced it by two other bases of computation, the cultivated crop acre and the adjusted crop acre.22 Replacing the crop acre by the cultivated Hall. Cost of Producing Rice in Arkansas in 1927; Saville and Reuss, Tractors and Trucks on Louisiana Rice Farms, 1929. 81 Reynoldson et al. " Figures on cultivated acres were already provided by Gilbert, in the New York study, but were not used as a basis for computations.

BASIS FOR C O M P A R I S O N S OF COSTS 169 acre prevents native hay, which requires the smallest amount of power, from appearing in the averages. Seeded grasses, however, retain their place therein. Moreover, the variations in the amount of power between all other crops are not eliminated, and may adversely affect the inferences. The authors themselves evidently placed the emphasis, not on the cultivated, but on the adjusted acreage. The adjusted acreage was computed by the authors of the Missouri study by using the horse work required for an acre of corn as the basis for reducing the acreage of the other crops to a corn-acre basis. Since the power requirements of corn were much higher than those of any other major crop, the number of adjusted crop acres per farm became considerably smaller than the number of crop acres. When cultivated and adjusted acres were used instead of crop acres for the farms investigated in the Missouri study, an average of 113.7 crop acres per horse farm was reduced to 64.9 adjusted acres (or to 73.7 cultivated acres), while an average of 168.0 crop acres per tractor-and-horse farm was reduced to 104.2 adjusted acres (or 132.3 cultivated acres). Thus there were only 57.1 adjusted acres to each 100 crop acres on the horse farms, while on the tractor farms, which had more crops with larger power requirements, the relation was 61.9 to 100. The difference in the cost of power, which on the basis of crop acres amounted to 5.3 percent in favor of the tractor farms, increased to 14.5 percent after the acreage was adjusted for the variations in the amount of power required by the various crops. 23 So far as drawbar power for growing and harvesting crops is concerned, the adjusted crop acre recommended by Smith and Jones impresses one as a very close approach to the solution of the problem of finding a proper basis for conclusions as to the superiority of tractors or horses for farm power. Only there 31 This percentage would be aeain diminished if the Missouri figures were computed for f;irms of equal size. If, however, only t h e l a t t e r changes w e r e made, the results of the c o m p u t a t i o n s , now f a v o r a b l e for t h e t r a c t o r s , w o u l d be probably reversed. T o s|>eak more generally, all reworkings of d a t a f r o m o t h e r studies, undertaken in ordor t o show the effect of the application of certain m e t h ods—for instance, t h e c o m p u t a t i o n of the cost of d r a w b a r w o r k per h o r s e - h o u r equivalent on Corn Belt f a r m s (see Chart 12) — are not considered b y t h e present writer as providing definite results. T o m a k e t h e m so, all r e c o m m e n d a t i o n s of this study would have to be applied simultaneously.

170 BASIS FOR COMPARISONS OF COSTS is no necessity for stopping so close to accomplishment, when nothing prevents making the last step. A very close approach to the solution of the problem is also found in 1934 Tractor Costs on 66 Michigan Farms, by Wright and Aylesworth. After the cost of power and labor per crop acre is computed in the usual manner, "the amount of power and man work to be done" per crop acre, based on the kind and amount of crops and livestock, is found. Finally, the costs per day of productive work are computed. Unfortunately no details of the methods used in those computations were given. T H E HORSE-HOUR EQUIVALENT AS T H E BASIS OF COMPARISON

We have shown that a comparison of the cost of power, made on the basis of crop acres, does not insure satisfactory results, even if the number of investigated farms can be considered a sufficient sample. Thus the possibility of making reliable comparisons of the cost of power stands and falls with the possibility of finding a proper foundation upon which to base the comparisons. We repeat that the adjusted acre, recommended by Smith and Jones, meets the requirements to a considerable extent. This proposal, generalized and simplified, may provide the desired solution. The adjusted acre of Smith and Jones is calculated by reducing the drawbar-power work, used for the growing and the harvesting of various crops, to the power required by corn or some other particular crop. It is possible to make this reduction only because the power work can be measured. But if an adequate measure for power work is available, why employ it only in an indirect way for conversion puiposes? It. would appear to be more expedient to use this same measure directly. From the procedure followed on pages 163-67 in analyzing the data of the Corn Belt study on the cost of drawbar power, it is evident that the horse-hour equivalent, occasionally used in power investigations for a long time, is a convenient unit for measuring drawbar work. It can, however, also be used as a measure of all other kinds of farm work. The recommended method of computing the horse-hour equivalent is discussed in the next section of this chapter. It may be stated here that the horse-hour equivalent cannot be considered an ideal meas-

BASIS FOR C O M P A R I S O N S OF COSTS 171 ure. The power of horses varies greatly in different countries and in different regions of the same countries. Some variations are encountered even from farm to farm. Moreover, the power of horses cannot be measured as exactly as that of power engines. The greatest care would be required for making the horse-hour equivalent sufficiently precise so that comparisons of studies made in different regions would be possible. An arbitrary element, also, is involved in the recommended procedure with regard to the conversion of belt work into horse-hour equivalents. Still, the uncertainties of the horse-hour equivalent can be made much less than those inherent in the other methods. We are inclined to consider the horse-hour equivalent as the only basis for getting a fairly reliable judgment on the superiority of tractors or horses as the source of farm power in those cases where doubt can be entertained in this regard. At first glance, it might seem possible to go still further and use the horsepower, equivalent to 550 foot pounds per second, developed for one hour, as the basis for all computations. The use of this measure, if possible, evidently would insure the greatest precision. However, as stated previously (p. 129), the use of the horsepower hour as the basis for computations is excluded by the fact that the relation of tractor work to horse work is different in various operations and on different farms. It varies according to the kind of soil, the size of implements, and proportion of different operations and of different crops. Mutatis mutandis, the same is true for trucks. Before leaving this subject, a few more general remarks are in order. It probably will occur frequently that data will be scantier and less reliable for the less important kinds of work (hauling, belt) than for drawbar field work. Consequently, the horse-hour equivalent is likely to be more dependable so far as drawbar work is concerned. It may be advisable, therefore, to make all computations, both for all power work combined and for the three important kinds of power work (hauling, belt, drawbar) separately. If the conversion of tractor drawbar work into horse work is found to be more reliable than that of the other kinds of work, the conclusions reached by investigators on drawbar power will be more accurate than those reached for other kinds of power. In the general discussion of the ap-

172 BASIS FOR C O M P A R I S O N S OF COSTS proaches to be used (see pp. 146-48). it was therefore recommended that the data on the cost of drawbar power per horsehour equivalent be always computed, and moreover be used as a starting point in the analysis, unless it would be found more advisable to start from a still earlier point, namely from a comparison between the cost of tractor drawbar work and of its equivalent in horse work. As the amount of work plays a very important role, the possibility has to be taken into consideration that some work would perhaps not be done if its full cost had to be charged to it. T h e necessary information could be secured by including an appropriate question or questions in the questionnaire. According to the nature of the cost of various sources of power (pp. 115-21), the likelihood that some unprofitable work is being done is greater with horses than with other sources of power. On the other hand, farms with partly or wholly mechanized power usually have a comparatively higher supply of power, and that which is abundant is more freely used. It is least probable that some unnecessary or unprofitable operations are being carried on in the case of field drawbar work; it is most probable in the case of hauling. This is another reason for separate treatment of the three kinds of power work on farms. T h e recommended method is of course not applicable in regions where the tractor has definitely replaced horses. This is the same situation which exists when regions without tractors are involved. N o r can horse-hour equivalents be computed unless data on the amount of work done on farms are available. T h i s probably is the case with the material concerning the farms in the Illinois study, on which the most, thorough investigation on f a r m power heretofore made has been based. COMPUTING HORSE-HOUR EQUIVALENTS

For attaining the greatest degree of exactness in computations of the horse-hour equivalents and horse equivalents of tractors and other sources of power, 2 ' the power of horses, to which the power of the other sources of power has to be related, ought to be determined as exactly as possible. This exactness ** When the w o r k of t r a c t o r s a n d other sources of power is computed in horse-hour equivalents, t h e horse equivalents of these sources of power are simultaneously established.

BASIS F O R C O M P A R I S O N S O F C O S T S 173 can be attained only by using a " h o r s e " of a certain size as the unit, determining the power of this horse with the greatest attainable precision, and converting the power of all different sources of power covered by the study, including that of horses, into that unit. Comparisons between the findings of different studies would be facilitated, if the power of a specific horse, for instance, that of a horse of from 5 to 8 years in age and weighing 1,300 pounds, were used as the unit in all studies. 2 "' T h e weight of horses, which is generally used as the indicator of the power of horses, is hardly a measure of the desired precision. At least the age also should be considered. Yet many more investigations would be necessary in order to determine accurately the relation between the weight and the age of horses, and the work done by them under farm conditions.'" T o the extent that the power of horses used on farms of different sizes and with different types of power is fairly uniform in a certain area covered by a study, the complicated reduction of the power of all horses to the unit can be avoided. T h e average power of horses in such an area should be established, however, in order to make possible comparisons with other studies. T h e computed horse equivalents would be only of restricted value, unless it were known whether they are expressed in the power of heavy horses or small mules. N o r can the computation of horse equivalents be regarded as satisfactory, unless the power of the tractors for which the comparison is being made, is known definitely. T h e same is true for all other sources of mechanical power. M a n y computations of horse-hour equivalents cannot be used because the power of tractors (and horses) involved is not stated or is stated but vaguely. The power of tractors ought to be indicated in adjusted horsepower, the power of all other sources of mechanical power likewise in horsepower, adjusted to the horsepower in tractors; i.e., for engines with internal combustion at 85 percent of their maximum belt horsepower, and for steamengine and electric-power accordingly. " These recommendations could not he f o l l o w e d in the c o m p u t a t i o n s m a d e by the present writer on pp. 163-67, because no data on the weight and the ag(-s of the hordes are provided in the Corn Belt study. " S e e Procter et ai, Efficiency of Work Horses of Different A get and Body Weights; and Brody and C u n n i n s h a m , Comparison between Efficiency of Ilorsc, Man, and Motor, with Specific Reference to Size and Monetary Economy.

174 BASIS FOR C O M P A R I S O N S O F COSTS It is evident that for each type and size of tractor (as well as other power machinery), separate sets of horse equivalents should be established. Moreover, it may be dangerous to have for each type and size of tractor only one set of horse equivalents. Types and sizes of farms have considerable bearing on the relationship between the performances of tractors and those of horses. Small fields hamper tractors more than they do horses. Large farms are likely to have implements better adjusted to their tractors, and therefore to have for the same tractors larger horse equivalents than small farms may have. Likewise tractors used as the auxiliary source of power usually have higher horse equivalents than tractors used as the principal source of power, since those tractors are utilized primarily for plowing and disking, while tractors used as the principal source of power perform many operations in which tractors are less efficient. Thus it may be necessary to compute the horse equivalents separately for each type and size group of farms. We shall call these horse equivalents group-horse equivalents. 27 The procedure of establishing the horse equivalents for all sources of mechanical power must start from individual performances. Direct comparisons of performances of mechanical power with those of horses, however, can be made only for trucks and for drawbar work of tractors. The work of all other sources of power can be compared directly only with the work of tractors. It is belt work and not drawbar work of tractors, however, with which the comparison is possible. Thus we have a gap: Performances of horses can be related only to tractor drawbar work; performances of miscellaneous sources of power only to tractor belt work. The gap can be filled only by establishing the relation between tractor drawbar and tractor belt work. The simplest method in this case probably would be to apply the same principle which has been chosen for charging the cost of tractor power to various kinds of tractor work (pp. 113-15). Investigators who intend to differentiate the charge for belt and for drawbar work ought to apply the same principle to the computations of horse equivalents of tractor power. If, for " Difficulty arises, in that group-horse equivalents have to be computed before the grouping of farms by size can be made, because the grouping by size is to be based on the amount of horse-hour equivalents (see next section). In grouping farms by size for computing horse equivalents, some rougher basis should probably be used.

BASIS FOR C O M P A R I S O N S OF COSTS 175 instance, the charge for belt work is set at 50 percent higher than that for drawbar work, the same percentage will reasonably apply when the horse equivalents of belt work are computed. So far as different charges for belt and for drawbar work are not acceptable, we recommend the use of the equivalents established for the same tractors in plowing, as the horse equivalents of belt work. An advantage of this procedure is that the horse equivalents of belt work will become somewhat higher than the average horse equivalents of the total drawbar work. Besides, if the average horse equivalents of the total drawbar work were used as the horse equivalents of belt work, the horse equivalents of the latter would be made dependent upon such circumstances as the proportion of light work to total work of tractors, which obviously is undesirable. After the relation between tractor drawbar and tractor belt work is established, the horse equivalents of tractor belt work and of the performances of miscellaneous sources of power may be easily computed. In comparing performances of tractors and trucks with those of horses, and the performances of other sources of mechanical power with those of tractors, caution must be observed. The time required for the same operation varies, depending on soil and topography. The possibility is not to be excluded that on heavy soils requiring more power or time tractors are more frequently used than on soils easy to work. On the other hand, horses probably are used more often on very stony ground, which also is difficult to work. Proper selection of the region for the investigation may, to a large extent, eliminate the risk of comparing figures affected by unequal conditions of this nature. Trucks, on an average, are used on better roads than horses, and the distances covered by them are greater. The ton-mile, therefore, cannot be used as the unit for converting truck hauling into horse hauling without some additional adjustments. The same farm operations may be performed more or less thoroughly under varying conditions, and will then require more or less power or time. This is particularly important as regards depth of plowing. In the South Dakota study 28 the following data are presented: " Hampson and Christophersen, op. cit., p. 22

176

BASIS FOR

COMPARISONS Horses

Plowing 2 14-inch 3 14-inch 4 14-inch

Number bottoms bottoms bottoms

5 8

Acres per Day 6 8.5

OF

COSTS

10/20 Tractor Acres per Day

15/10 Tractor Acres per Day

9 11.5

13.5 16.5

According to these data, teams of eight horses and 1 0 / 2 0 tractors with three-bottom plows cover 8.5 and 11.5 acres respectively per day. T h i s would be equivalent to the tractor's accomplishing the work of nearly 11 horses. Since 10/20 tractors arc not so powerful as this, it is safe to assume that, when plowing with three bottoms. 10/20 tractors penetrate to less depth than eight-horse teams. T h e 13.5 acres plowed by 1 5 / 3 0 tractors with three bottoms were possibly also plowed deeper than the 11.5 acres plowed by the 10/20 tractors. So far as depth of plowing (or cohesion of the soil) is concerned, the performances of the 10/20 tractors with three-bottom plows are possibly comparable only to the performances of 1 5 / 3 0 tractors with four plows. For comparisons with the performances of horses and of 15/30 tractors with three-bottom plows, only the performances of the 10/20 tractors with two-bottom plows seem to be appropriate. It may be observed from the above considerations that material difficulties arise in using data on plowing when the depth of plowing is not stated. T h e danger of confusion is large, even if, as in the case in South Dakota, no indications are present that the plowing with tractors is generally done to a different depth than plowing with horses. A bias is introduced still more easily, when the sources of power on southern farms, where deeper plowing with tractors seems tc be fairly videspread, are investigated. 2 9 T o render the comparisons of performances with tractors and horses reliable, the depth of plowing has to be ascertained in the schedules and considered in the tabulations. In computing the horse equivalents, the investigators have, of course, to consider the implements used on the investigated farms. T h e y must realize, however, that by so doing they a r e sometimes presenting a picture, not of the future, but at best of the present, and to some extent even of the past. T h e risk 29

See, e.g., Long's Farm

Pon er in the

Yazoo-Mississippi

Delta,

p. 29.

BASIS FOR C O M P A R I S O N S OF COSTS 177 in this case is particularly great that the whole study or some parts of it will become obsolete soon after publication or even before publication. For the horse equivalents of the same make of tractors increase, as time goes on. When a farmer buys a tractor, he frequently does not buy any implement to use with it except a plow. In all other operations tractors are worked with horse implements, with which the tractor is being utilized more or less inefficiently. Only after the horse implements have become worn out are they exchanged for tools constructed for use with the tractor in question. There are other ways, too, for increasing the horse equivalents of tractors. Both farmers using horse implements and those with tractor tools are endeavoring to work their tractors more nearly to capacity by combining operations (plowing and harrowing, plowing and seeding, disking and seeding, and so on). When it is not feasible to use larger implements, the matching of power and tools sometimes is attained by changing to a smaller tractor. 30 Where tractors have been introduced only recently, and the tendency of the horse-hour equivalents to increase is therefore strong, it may be desirable—apart from computations based on the present utilization of tractors—to make another set of computations which take into consideration the changes in performance that may be expected to occur in the near future. Some difficulties may result from the fact that the change from horse to tractor power frequently involves changes in operations. Some implements are used primarily or exclusively with tractors, others being retained in the domain of horses. The most significant examples are combined harvester-threshers and corn pickers, which are used with tractors much more frequently than with horses. Owing to the lack of data, there may sometimes be no alternative but to estimate the horse equivalents for the respective operations. After horse equivalents for each performance by groups of farms are established, the student has the choice of two ways. He may compute the average proportion of each perform""A further danger of obsolescence in data arises from the improvements which are being made in implements. Many a calculation has lost p3rt of its significance because, after the survey, binders with power take-off have been introduced, enabling one man to cut with a tractor considerably more acres than can be cut by two men with a tractor-drawn horse binder.

178 BASIS FOR C O M P A R I S O N S OF COSTS ance measured in time used to total time the tractors have been used on each group of farms dealt with separately, and then establish the group-horse equivalents for all performances of this group by weighting the group-horse equivalents for individual performances with these proportions. The preferable way, however, is to multiply the time spent for each performance of tractors, trucks, and so forth, on each farm, by the respective group-horse equivalent, and to derive from the resulting figures for each farm the horse equivalents in all performances, which we shall designate farm-horse equivalents. This method is indispensable if significance is ascribed to the figures for each farm, or if groupings of farms should be made other than those for which group-horse equivalents are being computed. From the farm-horse equivalents in all performances the composite group-horse equivalents in all performances can easily be computed. THE

HORSE-HOUR

EQUIVALENT AS THE M E A S U R E OF

SIZE OF FARMS I N POWER STUDIES

We have already indicated that different "acres" (crop acre, acre in rice, acre in cotton) are used in power studies as the basis not only for computations of the cost of power on farms but also for several other purposes, such as grouping the investigated farms by size and computing their average size. In other words, the crop acre is used in the computations of the cost of power because it is used for other purposes. Now, if the crop acre is replaced by the horse-hour equivalent as the basis for computing the cost of farm power, it seems appropriate to consider whether it would not be advisable to deprive it of its functions in some other computations as well. In the following chapter an attempt will be made to show the enormous effect of the size of farms on the unit cost of power. But the size of farms by itself, as measured in crop acres, man hours, or some other units, is not the determining factor for the unit cost of power, which is primarily the amount oj power work done on farms. Thus it seems expedient to use in power studies the selected unit of power (the horse-hour equivalent) also as the measure of size of farms (see also p. 208). Having chosen the horse-hour equivalent as the measure of

BASIS FOR COMPARISONS OF COSTS 179 farm size, the student has to decide what kind of power work should be used for this purpose. The total number of horsehour equivalents spent per farm or the number of horse-hour equivalents spent for drawbar field work only may be chosen. Yet some advantage may be gained from using as the basis for grouping farms by size either the amount of drawbar work for growing and harvesting plus hauling, in which case the total work of horses will be included, or else the amount of drawbar work for growing and harvesting plus belt work, thus including the entire tractor work. If one of these two methods should be selected, the deciding point will be whether the study is primarily devoted to horse or to tractor power.

VII

ADJUSTMENTS OF THE COST OF POWER POWER IS closely connected with all other factors of agricultural production, being affected by them and, to a still greater degree, in turn affecting them. T h e problem of the superiority of tractors or horses as the source of farm power cannot be solved by ascertaining merely the difference in the cost of power between tractor and horse farms. Only a few investigations of tractor use on farms, therefore, are restricted to the treatment of problems pertaining to power alone. Usually one or even several additional factors are considered. A D J U S T M E N T FOR LABOR

T h e performances of large crawlers are of such proportions that the expense for labor required for attending to power work becomes a small matter. Even the smallest agricultural tractor, however, with few exceptions, covers a larger area than teams of horses of usual size cover on similar farms, and hence involves a saving of labor. Moreover, before the depression, the saving of labor was frequently stressed, by farmers and. investigators alike, as the principal advantage of the tractor. N o study on the use of tractors on farms, therefore, was regarded as complete which, aside from the problem of power, did not at least consider the problem of the cost of labor. T h e depression and, to some extent, the curtailment of production effected by the Agricultural Adjustment Act greatly minimized the importance of labor. While less work had to be done on the farms, many farmers, because of the return of relatives from towns, had a more ample supply of family labor. Hired labor, however, did not disappear, even under the conditions of the depression, and recently even family labor has again become a matter of considerable value on almost every farm. Further improvement of the labor situation may be expected. 1 A saving in hired labor or an increase in income from custom 1 Black showed dearly the persistent tendency of farm wages to lag both in recovery and recession. "Agricultural Wage Relationships," pp. 3-10.

ADJUSTMENTS OF COST 181 work, made possible by the use of tractors, has obviously to be placed to the credit of tractors. An increase in acreage or in productive livestock, made possible by the use of labor released through the operation of tractors, ought to be treated likewise. Difficulties arise concerning the treatment of the time which, although saved by the use of tractors, is not utilized profitably. It is hardly possible to find universal answers to the questions whether, and if so, under what conditions and to what extent the farmer is inclined to pay for an increase in his leisure.2 When dealing with individual operations or individual crops, the adjustment for labor can be made only for each operation or each crop separately, and only on a per-hour or per-day basis. Such a procedure, it should be noted, makes it impossible to distinguish between time saved and used profitably and time which, although saved, is used only for leisure. In the earlier investigations, the time saved in attending to the work of tractors instead of that of horses usually was calculated in hours or days. By applying the current wage rate, the saved hours or days were computed in money and placed to the credit of the tractor. The tractors were consequently credited with all savings of labor, whether the saved labor was used gainfully or not. The findings were evidently biased in favor of tractors. In introducing the labor problem when dealing with the cost of power for all crops, the investigator may either use the described procedure or else may base his conclusions on the difference between the total amount of labor available on tractor and on horse farms. If the first method is chosen, the perhour charge for man labor usually is employed. In the second case, the monthly, seasonal, or even yearly charge is usually thought preferable. If the investigator chooses to place to the credit of the tractor the number of hours or days saved directly by utilizing tractors, the consequences are evidently similar to those mentioned in the preceding paragraph. In trying to avoid resulting biases by using the seasonal or annual charge for labor, the investigator is confronted with other, perhaps even 'Similarly, the question may be raised as to what extent the use of tractors is affected by the fact that many people prefer driving a tractor to driving horses. The preference in favor of the tractor is especially great if the alternative is driving a big team of horses.

182 ADJUSTMENTS OF COST greater, difficulties. To base the computations of the economy from the saved labor on a comparison of total costs of labor on tractor and on horse farms involves serious complications except on farms concentrating on crop production. Most farms are occupied not only with the production of crops, but keep productive livestock as well. The part of the labor which is used for attending to livestock is frequently considerable.3 Under these circumstances, if labor is to be taken into account, so also must livestock. So fraught with difficulties becomes the problem that some investigators consider it preferable to abandon the whole question of labor. If, however, the investigator deems it inadvisable to ignore this problem, he usually turns to data on the total cost of labor per crop acre, or on the total cost of power and labor per crop acre. In order to improve the conclusions drawn from these data, one or several adjustments are sometimes made. Data on the cost of labor per crop acre, like similar data on the cost of power, can hardly be relied upon for conclusions as to the superiority of different sources of power. Table 14 presents a comparison of the amount of labor used per crop acre in the Corn Belt for growing and harvesting various crops, compiled from the Corn Belt study.4 Although the variations in the amount of labor between different crops are not as large as those of the amount of power, they are. notwithstanding, very significant, the amount of labor used per crop acre of corn, on an average, being on horse farms nearly three times as great as that spent on hay. The labor requirements vary considerably, even with respect to the same crop, according to the method of seeding and harvesting. In many regions other than those devoted to wheat and rice production, the variations in the amount of labor per acre of various crops are still considerably larger than they are in the Corn Belt. There is, moreover, hardly any doubt that at least in the Corn Belt the variations in the amount of labor per crop acre, between groups of farms with different types of power, cannot 'Computations by Johnston and Wills (op tit., p. 312), for example, showed that farms with more than 300 acres in crops, which bought additional feed, spent nearly SO percent more labor than farms of similar size which fed only 20 percent of the feed raised on the farm. Even on farms with less than 80 acres, the relationship between the labor requirements of the two farm types was approximately 133 to 100. * Reynoldson et ai., Utilization and Cost of Power on Corn Belt Farms.

TABLE 14 LABOR USED PER CROP ACRE FOR GROWING AND HARVESTING CROPS I N T H E CORN BELT, AND ITS RELATION TO T H E A M O U N T O F P O W E R U S E D F O R T H E S A M E CROPS* Horse farms 1

Man hours

Percent man hours is of horse hours'

15.2 12.9 14.7 11.3 21.3 28.8 18.8

36.7 28.0 29.5 28.7 39.6 49.1 38.5

7.0

General-purpose tractor f a r m s

Man hours

Percent man hours is of horse hours®

11.2

29.6

9.0 7.3 16.4 18.4 11.8

19.8 19.2 29.1 37.7 28.5

37.8

6.0

42.1

6.0 11.4

43.2 45.8

5.3 d

41.1 d

d

d

8.1

41.3

6.6 8.0

44.0 44.4

5.5 6.2

42.6 41.6

10.9 d

38.9 d

9.2 7.4

32.0 29.8

9.8

33.1

8.1

31.6

8.9 8.1

67.2 33.4

Crop and method of production

CORN

Husked by Hand H u s k e d b y One-Row Horse Picker H u s k e d b y One-Row T r a c t o r Picker H u s k e d b y Two-Row T r a c t o r Picker C u t with Horse Binder for Silage C u t with Binder and Shredded Weighted Average OATS

E n d - G a t e Seeded b y Horses, H a r v e s t e d with Tractor E n d - G a t e Seeded b y Horses, H a r v e s t e d w i t h Horses Drilled a n d Harvested with Horses Drilled with Horses, Harvested with Tractor Broadcast with Horses, H a r v e s t e d with Horses Weighted Average WHEAT

Drilled and Harvested with Horses Drilled and Harvested with T r a c t o r Drilled with Horses, Harvested with Tractor Row Drilled with Horses, H a r v e s t e d with Tractor Weighted Average

d

d

10.9

.38.9

7.2 5.9 6.4 6.3

75.8 69.4 78.0 74.1

HAY"

With Loader from Swath With Loader from Windrow B y H a n d from Windrow Weighted A verage

" Source: Reynoldson et al., Utilization and Cost of Power on Corn Belt Farms, Tables 21, 22, and 23, pp. 52-53. 6 T h e d a t a pertain to farms designated in the Corn Belt study "Ordinary horse farms." e T r a c t o r work is converted into horse work b y assuming t h a t a tractor hour equals 10.0 horse hours on horse farms, and 7.25 horse hours on general purpose d tractor farms. Omitted, since d a t a for only one farm are given. • Horse farms and tractor farms.

184

A D J U S T M E N T S OF COST

be expected to disappear, even if a large sample is taken. On the contrary, farms of the same size which have much man work to do are more likely to keep tractors than farms with little man work, because they can more easily utilize the labor released by the tractor. Even the somewhat unsatisfactory adjustment of data on the cost of power, machinery, and labor on Illinois farms for variations in productive livestock (see Charts 8 and 9 on pp. 136 and 140) did not fail to make the comparison more favorable for tractors. A rather convincing proof of the assumption that the differences in the sources of power in the Corn Belt are not the only reason for variations, if such occur, in the cost of labor used per crop acre between groups of farms with different types of power is the fact that studies rather frequently show for some group or groups of tractor farms higher expenses for labor per crop acre than they show for horse farms. Since tractors always save some labor (the question is merely whether this saving is gainfully utilized or not), the larger labor costs per crop acre on tractor farms are a definite indication that the average combination of crops and livestock on the investigated tractor farms requires more labor per crop acre than the average combination of crops and livestock on the investigated horse farms. The resulting additional labor requirements on tractor farms are evidently larger than the saving of labor caused by the use of tractors. But in the Corn Belt there is likewise a tendency for farms with large labor requirements to use more frequently, aside from tractors, such important labor-saving machinery as combined hai vester-i.hr esheis and corn pickers, the economy from the saved labor having its counterpart in larger expenses on machinery other than tractors. Yet the comparison of the costs of labor per crop acre would favor tractors by crediting them with the economy attained by other kinds of machinery, even if this were supplemented by a comparison of the costs of the use of machinery. 5 Comparisons of power and labor, and even those of power, labor, and machinery, per crop acre are particularly biased in favor of tractors, if the combination tractor' Tractors can claim a share in the gains made by the use of combines and com pickers only in so far as these expensive machines can be utilized more fully when drawn with tractors.

ADJUSTMENTS OF COST 185 combine is confronted with the combination horses-binderstationary thresher in wheat growing.® It was shown in discussing the cost of power (pp. 168-70), that reducing the acreage in various crops to equivalent numbers of acres in corn on a horsepower basis considerably improves the quality of the data for use in conclusions as to the superiority of tractors or horses as a source of farm power. Unfortunately, the same basis cannot be used when dealing with the cost of power and labor, or with the cost of labor alone. The prerequisite for a conversion of the cost of labor per crop acre into the cost per acre in corn, on a horse-power basis, would be that the proportions between the amounts of labor and power be the same for all crops. But one man plows with a team of, say, five to six horses, while three men are necessary for cutting with a binder drawn by from three to four horses (the second and third men are for shocking). Moreover, the variations between the amounts of power and labor required for individual operations are not offset, even when the amounts of power and labor required for individual operations are combined in powerand-labor requirements of different crops. This is illustrated in Table 8 on page 143, in which the power, labor, and machinery requirements for growing and harvesting different crops in Missouri are related to the same requirements of corn. Smith and Jones,7 in dealing with labor, recommended the use of acres adjusted to equivalent numbers of acres of corn on a man-labor basis. So far as the production of crops is concerned, the acre, adjusted to an equivalent number of acres of corn, or of some other crop, on a man-labor basis, provides a means for ascertaining the amount of labor saved by using tractors. 3 The acre, adjusted on a man-labor basis, evidently has the same unnecessarily artificial character as the crop acre, adjusted on the basis of horse power. The crop acre, adjusted on a man-labor basis, also does not take care of variations in the " See the table on the cost of production of wheat in Western Kansas, reproduced by Tolley, " T o Determine the Economy of Using Tractors in a Specified Type of Farming Area," p. 209. ' Power, Labor, and Machine Costs in Crop Production, Linn County, Missouri, 1930. "From this amount, the amount of labor saved, but not used profitably, must be subtracted before conclusions can be drawn as to the amount of labor saved and gainfully employed.

186 ADJUSTMENTS OF COST amount of labor used for livestock, if any. In a somewhat reworked form, however, the method of handling the cost of labor proposed by Smith and Jones provides a proper way to adjust the cost of power on tractor farms for the economy from the saved labor. PROPOSED METHOD OF ADJUSTMENT

It is proposed that the cost of labor on farms with different types of power be not added to the cost of power, but that the latter be adjusted for the economy from labor saved by the use of tractors. This economy is computed by subtracting the amount of labor available on tractor farms from that which would be needed were the tractor farms horse farms. In order to arrive at the latter figure, it is first necessary to ascertain the amount of man work" used on horse farms for crops and livestock. This computation must be made in very detailed form, if fairly reliable results are to be attained. Not only must each kind of crop be treated separately, but also each kind of crop for which different practices in growing, harvesting, and so forth, are used. Each kind of livestock also has to be carefully subdivided into different enterprises (for example, cows kept for milk, cows kept for meat, and so on). The total amount of work to be done on tractor farms, if they were horse farms, is then computed and increased in the same ratio as labor available on horse farms is to work done thereon, in order to arrive at the amount of labor which would have to be available on tractor farms if they were horse farms.10 All these computations are in hours or some other unit of time. The second step is to compute the value of the time saved by the application of tne current wage rate. ' T h e term "work" is used in another sense than the term "labor." Work is labor actually used. Part of the labor available on farms always remains unused, owing to unfavorable weather conditions, seasonal distribution of operations, and so forth. " T h i s computation is based on the assumption that tractor farms, if they were horse farms, would show the same relation between available labor and work done as exists on horse farms. This assumption is probably true only for farms with very similar crop rotations and livestock enterprises. This limitation pertains also to the computation of labor saved, but not employed gainfully, which is discussed in the next paragraph of the text.

ADJUSTMENTS OF COST 187 The amount of labor computed by employing the procedure described above is labor saved and gainfully employedBy subtracting from the amount of labor available on tractor farms the amount of labor necessary on these farms if they maintained the same relation between labor available and work done as horse farms do, the amount of labor saved but not gainfully employed may be computed. The sum of the amounts of labor saved and gainfully employed and that saved but not employed gainfully is the total amount of labor saved by operating tractors.12 Under very favorable conditions, the amount saved and gainfully employed may be larger than the total amount of labor saved. This is the case when tractor farms succeed in having a smaller proportion of unused labor than horse farms. The proposed method is an attempt to use in power studies the productive man-unit, widely employed in farm-management studies as the unit for measuring the size of farm business. In reality, this method represents a generalization of the crop acre, reduced to equivalent acres in corn on the man-labor basis, much as the horse-hour equivalent is a generalization of Jones and Smith's crop acres, reduced to equivalent acres in corn on the power-work basis. In this generalized form the proposal takes care of all labor, including that used on livestock; consequently the necessity of looking for some specific adjustments for productive livestock is obviated.13 Moreover, apart from determining the amount of labor saved, the computation furnishes information as to the amount of labor saved and gainfully employed, as well as the amount saved but not employed gainfully. In a more systematic form, the procedure is as follows: 1. First, the amount of labor available on each size group and on each type-of-power group has to be computed. Let us designate it "Ah" for the horse farms of a certain size group, and " The expression "labor saved and gainfully employed" as used in the text includes disposed hired labor, although the hired men may not have found another occupation. u The same figure may be obtained also more directly, for example, b y subtracting the amount of work done on tractor farms from the amount of work that would have been done on them if they were horse farms, and by increasing the resulting figure in proportion of available labor to work done on horse farms. " The commonly used methods of making adjustments for livestock are discussed on pp. 195-97.

188 A D J U S T M E N T S OF COST "At" for the farms of the same size using a certain type of tractor. 2. Next, for each size group of farms the man work required for each crop, with further subdivision if different practices in growing or harvesting are followed, and for each kind of livestock also subdivided into different enterprises have to be computed. The computation of man work required for the crops, of course, ought always to be made separately for each size group of and each type-of-power group of farms, while the computation of man work required for the livestock sometimes may be made without regard to the type of power. Let the total amount of man work required on farms of the same size group, which is considered under paragraph 1 above, be "Bh" (horse farms) and "Bt" (tractor farms). Ah 3. represents the ratio between the amount of labor Bh available on horse farms and the amount of man work done on them. 4. By applying the amounts of work required on horse farms by different crops and different livestock enterprises to those on tractor farms, the amount of work which would have to be done on tractor farms if they were horse farms may be computed (Bti). Ah 5. Bt X = Ati, the amount of labor which would be Bh necessary on tractor farms, if the ratio between available labor and work done on them were the same as that on horse farms. Ah 6. Bti X = At2, the amount of labor which would be Bh necessary on tractor farms if they were horse farms. 7. At2 — At, = C, the total amount of labor saved on tractor farms. 8. At2 — At = D, the amount of labor saved and gainfully employed. 9. At — Ati = E, the amount of labor saved but not employed gainfully. In the schematic pattern presented in Table 15, it was assumed that tractor farms, if they were horse farms, would need,

ADJUSTMENTS OF COST 189 400 hours more work than they actually used (Bti — Bt); these 400 hours of work are equivalent to about 428 hours of I* Ail—1 available labor I (Bti — Bt) X — I. This is the amount of labor TABLE I S S C H E M A T I C P A T T E R N OF A COMPUTATION OF T H E SAVING OF LABOR RESULTING FROM UTILIZING TRACTORS

Horse farms AVAILABLE LABOR

Operator Hired Total

MAN WORK ACTUALLY DONE

On Crops On Livestock Custom Work off Farm Total

MAN WORK ON THE BASIS OF HORSE POWER

On Crops On Livestock Custom Work off Farm Total

10 5 15 3,750

months months months — hours (Ah)

1,500 hours 2,000 hours 3,500 hours (Bh) 1,500 hours 2,000 hours 3,500 hours (Bh)

Tractor farms 10 5.5 15.5 3,875

months months months — hours (At)

1,000 2,300 125 3,425

hours hours hours hours (Bt)

1,400 2,300 125 3,825

hours hours hours hours (Bti)

Hence: The amount of available labor on tractor farms which would be necessary if the ratio between available labor and work done were the same on them as on horse farms:

I Bt Ati J = 3,670 hours. \ Bh The amount of available labor on tractor farms which would be necessary if they / Ah were horse farms: I Bti =Atj J = 4,098 hours. Bh \ Total labor saved by tractor farms: (Atj—Ati«C) = 428 hours. Labor saved and gainfully employed on tractor farms: (Atj—At = D) = 223 hours. Libor saved but not employed gainfully: (At—Ati=E) = 205 hours.

saved on tractor farms by using the tractor (C). After the other necessary computations have been made, these 428 hours are split into 223 hours of labor saved and gainfully employed (D) and 205 hours of labor saved but not employed gainfully (E). If the comparison shows that tractor farms have failed to

190 A D J U S T M E N T S OF COST make a money saving on labor, the question naturally arises as to why they have failed. It is possible that the farmers were able to make a saving, but did not wish to do so because the purpose, or one of the purposes, of acquiring tractors was to diminish the strain on the family labor. The other conjecture is that the farmers were prevented from utilizing the saved time by a lack of opportunity for custom or some other work. This will happen frequently if a considerable peak of labor occurs which does not coincide with the peak of power requirements eliminated by utilizing the tractor. We cannot dwell further on the problem of the seasonal distribution of labor (and power) requirements. There is, however, no doubt that it cannot be ignored in power studies. Suitable questions in the questionnaires may secure some data on the reasons why the labor which is saved by the utilization of tractors, or part of it, is not employed gainfully. A D J U S T M E N T FOR M A C H I N E R Y "

A two-bottom plow, constructed for work with tractors, is more expensive than a similar plow to be drawn by horses. The same is true for almost all other agricultural machinery. The cost of tractor machinery, computed on a per-acre basis, may nevertheless be smaller than that of horse machinery, because the area covered by tractor machinery in the same time frequently is increased at a higher rate than is the price. A condition for lower costs per acre is that the number of hours that tractor machinery is used per year should not be less than that of horse machinery. Frequently, however, this condition is not fulfilled, owing to the smallness of the farms. Another reason for the smaller utilization of machinery on tractor farms is that farmers, when buying a tractor and tractor implements, may own serviceable horse machinery which is retained after the purchase of the tractor. Farmers using both tractors and horses as sources of power frequently are compelled to keep both horse and tractor machinery. All these divergences are obviously caused by the use of tractors on tractor farms. Conse" The expression "machinery" in general does not include power machinery in this study. Exceptions have been necessary when data from other studies, in which the term "machinery" does include power machinery, have been reproduced.

ADJUSTMENTS OF COST 191 quently, proper comparison between the cost of tractor and horse power may make it necessary to consider also the cost of the use of machinery. If the comparison between different sources of power is made on the basis of costs per crop acre, there are still more factors calling for adjustments of these costs for differences in machinery. Tractor farmers more often own combines than do horse farmers. In this case, the saving in the cost of power and labor per acre owing to the use of combines is accompanied by increased per-acre costs of machinery. The situation is reversed with regard to corn pickers, which also are oftener found on tractor farms. Since the cost of the use of machinery usually is rather small, as compared with the cost of labor, the disregarding of the variations in the cost of machinery on different type-of-power farms is far less damaging to the conclusions drawn than is the omission of labor. This statement does not, however, apply to such situations as are encountered, for example, in wheat growing, where the difference in investment between combines and binders is very large. While an adjustment for variations in the cost of the use of machinery caused by operating tractors is usually less urgent, it likewise does not imply such great difficulties as are introduced by the cost of labor. For, contrary to the case with labor, the number and kind of productive livestock affect the cost of the use of machinery but slightly. Adjustments for the cost of machinery are made in both the ways described above. Either the computed cost of tractor work is adjusted for the savings or the additional expenses on machinery, or else the cost of using machinery is simply added to the cost of power on both sides of the comparison. In the latter case, it again is the crop acre which serves as the basis. If, apart from the cost of machinery per crop acre, the cost of labor also is added to the cost of power per crop acre, the resultant figure represents the total cost of power, labor, and machinery, which in many power studies is the cornerstone of the argument. The cost of the use of machinery per crop acre is no more helpful in power studies than the similar costs of power or labor. The first cost of various kinds of machinery varies widely. The expense for machinery per acre also varies con-

TABLE 16 COST OF M A C H I N E R Y P E R CROP ACRE FOR GROWING AND HARV E S T I N G C R O P S I N L I N N C O U N T Y , M I S S O U R I , 1930, A N D ITS RELATION TO T H E AMOUNT OF POWER USED FOR T H E SAME CROPS'

Farms using horses Crop and method of production

Farms using tractors and horses

Cost of Percent Cost of use of machine use of machin- cost is machinery in of power ery in dollars cost dollars

Percent machine cost is of power cost

CORN

1. Disked Cornstalks and Drilled; Horse Power Used 2. Horse Power Used, Two-Bottom Plows, Single and Double-Row Cultivators 3. Tractor and Horse Power Used to Prepare Seed Bed 4. Tractor Power Used, except for Planting and Part of Cultivating OATS

1. Horse Power Used; Sown Broadcast 2. Horse and Tractor Power Used; Sown Broadcast 3. Same as (1), except Sown by Drill 4. Those Who Hired Some Field Work Done

1.03

22.8

0.93

20.6

0.59

40.1

1.40

71.1

0.27

18.4

0.87

62.6

0.99

23.6

0.72

21.6

0.47

32.6

0.63

36.8

0.75

29.4

WHEAT

1. Disked Cornstalks and Drilled; Horse Power Used 2. Same as ('), except Hcrse and Tractor Power Used 3. Ground Plowed and Drilled; Horse Power Used 4. Same as (3), except Horse and Tractor Power Used

0.98

26.8

" Smith and Jones, Power, Labor and Machine Costs in Crop Production, Linn County, Missouri, 1930. Threshing is not considered in the computations.

TABLE 16

(Continued)

C O S T or M A C H I N E » * P E R C R O P A C R E FOR GROWING AND H A R V E S T I N G C R O P S IN L I N N COUNTY, M I S S O U R I , 1 9 3 0 , AND I T S R E L A T I O N TO THE A M O U N T o r P O W E R U S E D FOR THE SAME C R O P S

Farms using horses Crop and method of production

SOV BEANS

1. Hauled to Bam; Horse Power Used 2. Hauled to Barn; Horse and Tractor Power Used 3. Stacked in Field; Horse Power Used 4. Stacked in Field; Horse and Tractor Power Used 5. Threshed for Seed; Horse Power Used 6. Threshed for Seed; Horse and Tractor Power Used

Farms using tractors and horses

Cost of Percent Cost of Percent use of machine use of m a r h i n p machin- cost is machin- cost is ery in of power ery in of power dollars dollars cost cost 0.88

26.6

1.02

39.4

1.28

33.2

0.89

24.0

.69

47.3

.82

47.1

.18

20.7

HAY, TIMOTHY, AND CLOVER

1. Pitched on Wagon by Hand; Unloaded at Mow by Power 2. Same as (1), except Hay Loader Used 3. Stacked in Field; Sweep Rake Used; Hand Pitched 4. Same as (3), except Stacker Used 5. Baled in Field; Sweep Rakes Used

.26 .82

27.1 107.9

.33 .40 .52

73.3 72.7 51.0

1.12

47.5

.55

74.3

ALFALFA HAY

Handled Same as (1) Above TIMOTHY SEED

Cut with Horses and Binder Cut with Tractor and Binder

194 ADJUSTMENTS OF COST siderably from crop to crop. It may be seen in Table 16, computed from the data of the Missouri study,15 that variations in the cost of machinery per crop acre are large not only for various crops, but even for the same crops, if different practices are followed. For instance, the cost of machinery per acre of oats on horse farms is 59 cents if they are sown broadcast, and $1.40 if they are drilled. Although the cost of the use of machinery per acre for different crops varies less than does the cost of power computed in the same manner, the cost of machinery per crop acre, like the cost of labor and the cost of power per crop acre, does not provide a safe basis for comparisons of the cost of various types of power. The ratio between the cost of the use of machinery and the cost of power per crop acre varies, according to Table 16, from about 20 percent in the case of corn to over 100 percent in the case of hay pitched on a wagon with a loader. Thus the crop acre adjusted for the amount of power likewise could hardly be used as a substitute for the crop acre, in adjusting the cost of power per crop acre on different type-of-power farms for variations in the cost of the use of machinery, caused by the differences in types of power. The value of conclusions as to the profits attainable by the use of tractors, derived only from figures on the cost of power on tractor-and-horse farms, without considering the cost of machinery, is greater when the cost of power is computed per horse-hour equivalent than when crop acres are used as the basis of the computations. The fact that tractor farmers utilize more corn pickers, which impairs the comparisons of the cost of power per crop acre, cannot affect the comparableness of the data computed per horse-hour equivalent. The same applies to the utilization of combines, so far as the risk of biasing the result in favor of tractors is concerned.16 Thus leaving machinery out of consideration in power studies would be less dangerous if horse-hour equivalents were used than when crop acres are the basis of comparison. If it is desired to consider machinery, the procedure ought to "Smith and Jones, op. cit. "However, since combines work more efficiently with tractors than with horses, to disregard the fact that tractor farmers use more combines would result in omitting one of the inducements for acquiring tractors.

A D J U S T M E N T S OF COST 195 be similar to that followed with regard to power and labor. For each crop (subdivided into groups with different production practices), the cost of machinery per acre on horse farms of each type and size group should be computed. By applying these findings to the acreage of each crop grown on tractor farms, it is possible to compute what the cost of the machinery would be, if they were horse farms. A comparison of the actual costs of machinery on tractor farms with those computed costs will provide information as to additional cost or saving on machinery on tractor farms as compared with horse farms. The variations in the amount of livestock between tractor and horse farms probably may frequently be disregarded entirely, so far as the cost of the use of machinery is concerned. But if these are to be considered, the average cost of the machinery required for each kind of stock may be computed, and adjustment made for variations in these costs in various groups. Thus data for all three main factors—power, labor, and machinery—would be reduced from a cost basis to an amount basis, and probably might be relied upon for conclusions as to the superiority of tractors or horses as the source of power. A D J U S T M E N T FOR L I V E S T O C K

The method proposed above for dealing with labor in power studies (pp. 186-90) also provides for variations in the amount of labor used on livestock. If desired, the effect of variations in the amount of livestock on the cost of the use of machinery may be eliminated in a similar manner, as stated above. Thus it remains only to consider briefly the methods used by other writers for adjusting the data on the cost of power for the labor and machinery costs of livestock. When the cost of power and labor (and machinery) is adjusted for variations in the amount of livestock, it is done primarily for the purpose of eliminating the differences in labor (and machinery) spent on livestock on tractor and horse farms. In making those adjustments, however, animal units, computedon the basis of feed required by the various kinds of livestock, are commonly used as the basis for conversions. This basis obviously has nothing to do with either power or labor. Feed required for a milk cow and a beef cow may not vary greatly, yet the difference in labor requirement is considerable.

196 A D J U S T M E N T S OF COST The authors of the Illinois study used data on the value of the feed fed to productive livestock, for eliminating variations contingent upon livestock. Charts 8 and 9, pp. 136 and 140, show the rather substantial changes in these costs which result from the adjustment for livestock. Most affected are the 1931 costs on horse farms with 40 to 79 acres in crop». Before the adjustment, these costs were lower than on general-purpose tractor farms of the same size by $2.17 per crop acre, while they are higher by 68 cents according to the adjusted figures (see Chart 8). Another significant change is that, in the figures for 1931, the difference in costs between ordinary tractor farms and general-purpose tractor farms of the smallest size groups is reduced by $2.52 per crop acre by the adjustment (see Chart 9). Moreover, the adjustment for productive livestock undoubtedly introduced some improvements in the original data. For example, the reduction in the 1931 costs of the difference between ordinary tractor and general-purpose tractor farms of the smallest size group (Chart 9) impresses one as very reasonable. The same can be said of the reduction in the difference of costs in the largest size group in 1930, shown in Chart 8. Yet the discrepancies discussed on pp. 139-42 in part became even larger after the adjustment was made. The inconsistent tendency of the costs on general-purpose tractor farms, as compared with ordinary tractor farms, to become less favorable for the former with the reduction in the size of farms, as revealed by the adjusted 1930 figures for all size groups but the smallest, did not appear in the original figures (see Chart 9). Some changes, caused by the adjustment in the data of Chart 8, likewise do not strike one as very reasonable. The fact that the cost of horses, labor, and machinery on Illinois farms, adjusted for productive livestock, failed to reveal relations which should be definitely expected is probably to a large extent the result of the deficiencies of the original unadjusted data (their having been computed per crop acre). Yet an adjustment for productive livestock in the usual manner, namely, in the form of an adjustment for the number of animal units or for the value of feed fed (substituted in the Illinois study, instead of animal units), also is inadequate for the purpose in mind. The reasons do not require further elaboration.

A D J U S T M E N T S OF COST 197 The authors of the Illinois study, Johnston and Wills, tried to ascertain whether the labor saved by the utilization of tractors was used for improving the quality of the livestock, by means of analyzing the returns per $100 of feed fed to livestock. Our recommendation for handling labor in power studies probably would eliminate the necessity of this computation, since it provides for a detailed subdivision of the livestock by kinds (e.g., in cows kept for meat; in cows kept for milk, with milk sold in the form of butter fat; in cows kept for milk, with milk sold fresh; and so forth). A change from cattle kept for meat to milk cows; from milk sold in the form of butter fat to milk sold fresh; and similar changes which are not reflected in the usual animal units but are considered in the recommended computation both increase the returns per $100 of feed fed and require more labor, power, and machinery per animal. A D J U S T M E N T FOR Y I E L D S

Most investigators assume that higher yields on tractor farms are probable. Tractor farms usually have more power per acre than horse farms. When necessary, tractors can also be worked longer hours, and even day and night. It is generally accepted, therefore, that tractor farms are in a more favorable position, so far as timeliness of work is concerned. Moreover, the greater supply of power enables tractor farmers to include some additional operations, or to perform some operations more thoroughly. Extensive use of this opportunity is probably being made on farms in the South, where the tractor frequently replaces the one-mule power.17 The same is true to some extent for some other regions. Stephens writes, in the Oklahoma study: 18 "It was noticeable that, as a rule, the seed bed was given more timely preparation and more operations were performed, for example, an extra disking, on the tractor-operated farms than on the average horse-operated farms." This remark pertains to wheat-growing Garfield County, which does not belong to the "South." Nevertheless, it seems likely that in regions other than the South, more operations or more thorough operations on tractor farms are rather the exception than the rule. "Long, op. cit., p. 29. "Op. cit., p. 30.

198 A D J U S T M E N T S OF COST The one major disadvantage of the tractor, as regards quality of work done, is loss of manure in regions where manure is important and displaced horses are not replaced by productive stock. In spite of this reasoning, adjustments for higher yields on tractor farms could be made only occasionally. The number of farms and/or years for which data were secured frequently was not sufficient for a comparison of yields. So far as such comparisons were believed feasible, it was impossible to eliminate the simultaneous effect of other factors, especially the variations in the quality of the soil. On the Oklahoma farms, for example, to which the above quotation pertains, wholly mechanized and tractor-and-horse farms in 1931, on an average, harvested 20.6 and 21.6 bushels of wheat per acre respectively, while on the horse farms the yield was only 16.2 bushels. But "the farms using only horses tended to be the smaller farms in the poorer areas," and "the land on the horse-operated farms was valued at only $45 per acre in comparison with $60 and $65 per acre in the other groups." Thus the question was unanswered as to what part the tractors had in the higher yields. But if an increase in yields on tractor farms can be unquestionably attributed to the tractor itself, it ought of course to be put to the credit of the tractor, the tractor being charged at the same time with the cost of the additional work incurred. This charge ought to include not only the cost of additional work in preparing the seed bed or in caring for standing crops, if any, but also the cost of harvesting, hauling, and so forth, incurred for the additional product. An adjustment for yields, if made, would not improve the comparableness of figures on the cost of power, computed per crop acre, since an adjustment of the cost of power (and/or labor and/or machinery) for yield can replace an adjustment for the amount of power (and/or labor and/or machinery) only to a small extent. Timeliness of work increases the yields without any additional application of power, often even with a simultaneous saving in power. And additional operations and more thorough operations on tractor farms probably are relatively unimportant so far as the whole country is concerned. An adjustment for yields should thus be made only after the figures on cost of power are securely based on amounts of power used.

VIII

THE EFFECT OF FARM SIZE ON THE COST OF POWER A M O U N T AND C O S T OF P O W E R AS A F F E C T E D BY F A R M S I Z E T H E A M O U N T of power work normally increases at a slower rate than does the size of farms as measured in crop acres. This decline is equivalent to a smaller amount of power work per crop acre on larger farms. All three kinds of power work (drawbar, belt, and hauling) are involved. Several factors bring it about that small farms commonly use more drawbar power for growing and harvesting crops than do large farms. Smaller fields, improper machinery, and similar reasons cause a less efficient utilization of power, particularly of tractor power, on small farms. But commonly small farms also have a greater proportion of land in crops with greater power requirements. These circumstances, as well as the usually greater number of livestock per crop acre, result in more belt work per crop acre on small, as compared with large, farms. The greatest difference between small and large farms in the amount of power used per crop acre is generally in the amount of hauling of crops and livestock, and especially in the amount of power spent for occasional trips. The decline in the amount of power work per crop acre on farms of greater size is smallest in regions producing only small grains and having only a relatively small amount of productive livestock; it is largest in mixed farming, where small farms to a greater extent adhere to intensive lines of animal husbandry (for example, fresh milk deliveries) than do large farms. The decline in the amount of power work per crop acre does not proceed indefinitely. It does not, however, terminate sharply on the largest farms covered by power studies. On the two-plow tractor farms included in the Corn Belt study, 1 for example, farms with from 100 to 179 acres in crops on an average used 27.31 horse-hour equivalents per crop acre for field work, which 1

Reynoldson et al., op. cit., Table 4.

200 E F F E C T OF FARM SIZE ON COST was 8.9 percent more than was used on farms with 260 and more crop acres. The two-plow tractor farms, with from 100 to 179 crop-acres, used 0.227 hours of owned tractor for belt work per crop acre, or 111 percent more than the farms with 260 and more crop acres. The same groups of farms used 0.211 hours of owned truck per crop acre, or nearly eight times more than the larger farms. Horse farms with 300 and more crop acres on an average used a total of 26 horse hours per crop acre, while horse farms with less than 60 crop acres used 43 horse hours. The same farms used per crop acre 0.065 and 0.163 hours, respectively, of hired tractor belt work. Unfortunately, no data are at hand on variations in the amount of hauling per crop acre, which probably are still greater than those of the other kinds of power work. Not only the amount of power used per crop acre, but the cost of power per hour (horse hour, tractor hour, horse-hour equivalent) as well, declines as the size of farms increases. Large farms commonly use each of their sources of power more hours per year than do small farms, and this obviously reduces the cost per hour. The difference between large and small farms is particularly great with regard to the number of hours that tractors are used per year, this figure being sometimes three and four times as large for large farms than for small farms. So far as the cost of power is computed per horse-hour equivalent, the higher cost of power on small tractor farms is also caused by the fact that the work of tractors on these farms is equivalent to the work of a smaller number of horses than it is for similar tractors on large farms. As in the case of the amount of power, the rate of the decline in the cost of power per hour differs on farm groups with different types of power. Farm organization and the kind of products turned out also materially to affect this rate. Hence, if the cost of power per hour on farms of different sizes is presented in the form of curves (see Chart 13), as many curves may be obtained as there are farms. But the common form of the curves is a steep decline at first, which becomes ever slower as the total amount of power work on the farm increases.2 Finally a 'The total amount of power work is used in Chart 13 as the measure of the farm size (see pp. 220-22).

CHART 13 COST OF HORSE AND TRACTOR POWER P E R HORSE-HOUR EQUIVALENT ON FARMS WITH D I F F E R E N T AMOUNTS OF POWER WORK

Assumptions Horse Curve A. The number of hours that horses are used during the year increases from 375 at 750 horse-hour equivalents of total power work to 800 at 4,800 and more horse-hour equivalents. Horse Curve B. The number of hours that horses are used during the year increases from 375 at 750 horse-hour equivalents of total power work to 2,000 at 10,000 and more horse-hour equivalents. Tractor Curve A. The data are for tractors with steel wheels and with 10-11 adjusted drawbar horsepower. The efficiency of the tractors advances from 6.75 horse-hour equivalents, at a total annual power work up to 1,300 horse-hour equivalents, to 7.75 horse-hour equivalents at a total annual power work of 6,000 and more horse-hour equivalents. The number of hours that tractors are used during the year does not increase beyond 800. Tractor Curve B. The size of tractors increases from 10-11 horsepower to 20-22 horsepower as the total amount of power work increases. The efficiency of the tractors increases similarly to that of Tractor A. The number of hours per year is handled in the same manner as for Tractor A. For prices used and method of computing the cost of horse power, see Table 7, p. 118. Prices and method of computing cost of the tractor with 10-11 horsepower are given in Table 6, p. 116. The method used for the larger tractors is outlined in Chapter IV; prices except of those for the tractors are those given in Tabic 6. The cost of farm power per horse-hour equivalent, or any other time unit, is strongly affected by the total amount of power work that has to be done on the farm. The particular source of power used to perform this work is of considerable influence only on the rate of the decline of the cost at different amounts of total power work, and on the limit to which the decline extends. In general, the decline of the cost of tractor power is stronger and proceeds further than that of the cost of horse power. This is especially the case when larger tractors can be substituted for smaller ones on farms with much power work.

202 E F F E C T OF FARM SIZE ON COST stage is reached where the curve is horizontal, or nearly so.3 Actually, the curves showing the cost of power per hour on farms of different sizes decline in a zigzag. The zigzag is caused by adding more horses and tractors. Every time such an addition is made, the number of hours that horses or tractors are used per year declines abruptly and the cost per hour abruptly increases. The cost of power per crop acre is the product of the amount of power used per crop acre, times the cost of power per hour. It is evident that since both determining factors tend to decline as the size of farms increases, their cumulative effect on the cost of power per crop acre will be even more pronounced. According to Reynoldson et al.,* in 1929 expenses for total power ranged from $8.51 per crop acre on horse farms with less than 60 crop acres to $4.14 on similar farms with 300 and more crop acres. On farms with ordinary three-plow tractors, the range was from $9.93 on farms with less than 100 acres to $4.41 on those with 300 and more crop acres. Even when the farms with less than 100 crop acres are disregarded, the range in cost of power per crop acre remains wide: Type-of-Power

Groups

Ordinary Two-Plow Tractor Farms Ordinary Three-Plow Tractor Farms General-Purpose Tractor Farms Ordinary Horse Farms

Cost o] All Power per Crop Acre on Farms with: 100 to 139 Crop Acres $6.30 7.02 6.31 5.70

300 and More Crop Acres $3.95 4.41 3.4S 4.14

The smallest difference in the cost of power per crop acre, between farms with 100 to 139 acres in crops and those with 300 and more crop acres, was that encountered on ordinary horse farms. It still amounted, however, to $1.56 per crop acre, or to 37.7 percent of the cost on large farms. On an average for all type-of-power groups, the cost of power on farms with from 100 to 139 crop acres was 55.2 percent higher than on farms with 300 and more crop acres. ' A s in the situation with respect to the amount of power, the decline in the cost per horse-hour equivalent does not proceed indefinitely, but usually does not terminate on the largest farms included in the power studies. * Utilization and Cost of Power on Corn Belt Farms, pp. 45, 48.

E F F E C T OF FARM SIZE ON COST 203 The significance of these figures becomes apparent when they are compared with the variations in the cost of power on farms with different types of power. Out of the three type-of-power groups of tractor farms considered in the Corn Belt study, the cost of power on the three-plow tractor farms deviated most widely from that of the horse farms. Taking the two size groups of those type-of-power groups which show the largest deviations,5 we find that the difference in the cost of power per crop acre amounted to $1.32 and $1.65 respectively, in favor of the horse farms. On farms with from 180 to 219 crop acres, it was $1.04 for the same type-of-power groups. Apart from these extremes, the difference in the cost of power, between horse and tractor farms of similar size groups, was in no case greater than 78 cents. The difference in the cost of power between tractor and horse farms becomes nearly negligible, if the costs of power on farms with different types and sizes of tractors in each sizeof-farm group are averaged; for farms with 300 and more acres in crops it amounts only to 20 cents in this case. Thus the effect of the size of farm on the cost of power per crop acre in the Corn Belt is many times greater than the effect of the type of power. This is shown in Chart 14, where the cost of power per crop acre on all type-of-power groups of farms with more than 100 acres is expressed in percentages of the average expenses of the groups with 300 and more crop acres, the cost of power on all type-of-tractor farms being expressed in percentages of the cost for horse farms. In regions where the variations in crops grown and the differences in power requirements between various crops are less than in the Corn Belt, and where animal husbandry does not play a great role, the power requirements per crop acre vary less with the size of farms, but the variations apparently are considerable everywhere. Whether the influence of the size of farms on the cost of power be greater or smaller than the influence of the type of power, the effect of the size of farms on the cost of power per crop acre is so elemental that, in case it is not eliminated, the findings are likely to be strongly biased in favor of one of the sources of power, in most cases in favor of ' These are the groups of three-plow tractor and horse farms with from 100 to 139 and from 140 to 179 crop acres.

S I Z E G R O U P OF F A R M S ( C R O P A C R E S )

•I Two-plow tractor farms EJ General-purpose tractor farms

EgJ Three-plow tractor farms E23 Ordinary horse farms

CHART 14 VARIATIONS IN THE COST OF POWER PER CROP ACRE ON FARMS OF DIFFERENT SIZES AND WITH DIFFERENT TYPES OF POWER, CORN BELT, 1929 Data from Reynoldson et al., Utilization and Cost of Power on Corn Belt Farms. The size of farms affects the cost of power per crop acre in the Com Belt much more strongly than does the type of power. Data on the cost of power per crop acre, from which the influence of variations in the size of farms is not eliminated, are therefore not a proper basis for conclusions as to the superiority of different sources of power.

206 E F F E C T OF F A R M S I Z E ON COST tractors. When different tractors are compared, the disregarding of the effect of farm size on the cost of power is likely to favor one type of tractor to the disadvantage of another type. Despite the great influence of the size of farms upon the variations in the cost of power, this factor is usually not given the proper amount of attention. In Table 33 of the Prairie Provinces study, 6 which is reproduced in part in Table 17, the TABLE 17 E F F E C T OF TRACTORS ON ACREAGE AND ON T H E N U M B E R HORSES DISPLACED ON WHOLLY MECHANIZED FARMS IN T H E PRAIRIE PROVINCES OF CANADA'

Size of tractor

Three-Plow Four-Plow Over Four-Plow

Number of farms in group

16 12 3

Before purchase of tractor

After purchase of tractor

Cultivated acres

Horses

Cultivated acres

355 366 640

11.2 10.3 14.0

640 648 1,013

OF

Real reIncrease duction in the numin ber of acreage horses 285 282 373

° Source: Hopkins et ai., Cost of Producing Farm Crops in the Prairie Table 33, p. SO.

20.2 18.3 20.9 Provinces,

effect of the tractor in reducing the number of horses and in changing some other items on horseless (wholly mechanized) farms is computed. According to Table 17, the "real" reduction in the number of horses on three-plow tractor and four-plow tractor farms was equivalent to 20.2 and 18.3 horses respectively. These figures were arrived at by dividing the cultivated acreage of those farms after the purchase of tractors and the extension of their cultivated area (640 and 648 acres, respectively), by the number of acres cared for by horses on the same farms before the purchase of tractors and the extension of the cultivated area. It is remarkable, however, that 20.2 and 18.3 horses, respectively, could be saved by farms whose cultivated acreage amounted to 640 and 648 crop acres after purchase of tractors, ' H o p k i n s et al., op. cil., p. SO.

E F F E C T OF FARM SIZE ON COST 207 while the farms with over-four-plow tractors actually had only 14 horses for 640 cultivated acres before the purchase of tractors. It is evident that had the three-plow tractor and the fourplow tractor farms increased their crop acreage to 640 acres without the purchase of tractors, the number of horses required by them would hardly increase in proportion to the increase in acreage. For in the higher size group, where they would then have belonged, a horse usually takes care of a larger number of acres. The Missouri study7 did not take into consideration a rather large difference in size between its tractor-and-horse farms and horse farms, not only in computing the number of displaced horses, but also in calculating the saving of labor,8 the number of hours worked per horse, and the cost of horse work per hour. Most investigations do not disregard the effect of the size of farms on the cost of power. On the contrary, it is rather a common practice to divide the investigated farms into groups according to the size of farms. Sometimes so many groups are established that the number of farms in some becomes too small to preclude the possibility of accidental results. The procedure commonly employed in power studies, nevertheless, can be improved substantially. Of the few studies containing an unbiased treatment of the size of farms, the Illinois study takes first rank. Johnston and Wills, the authors, state: 9 It is clear that any comparison of costs of different types of power should be based on cost within comparable size groups. Unless the comparison is limited in this way, the smaller size of horse farms puts them at an unwarranted disadvantage, since larger farms, whether operated with horses, standard tractors, or general purpose tractors, can be operated with lower labor, horse and machinery costs per acre, than smaller farms.

The authors might have mentioned that the usual manner of handling data on farm size not only frequently creates biases * Smith and Jones, op. cit., p. 16. "The amount of labor saved owing to the use of tractors was greatly exaggerated (the authors arrived at a saving of 45 percent), also because the computation was made as though the amount of productive livestock on larger farms were greater than on small farms, in exact proportion to their crop acreage. 'A Study of the Cost o/ Horse and Tractor Power on Illinois Farms, p. 278.

208 E F F E C T OF FARM SIZE ON COST against but sometimes also in favor of horses. The latter biases, it is true, usually are less significant.10 Several important conclusions ought to be drawn from the general considerations presented above. It seems appropriate to start from a somewhat specific one, in order to clear the way for the subsequent discussion. Moreover, the subject involved (the unit of measurement for the size of farms) has already been discussed (see pp. 178-79) and a few additional remarks will suffice. No other unit besides the crop acre can be used as the measure of farm size in studies using the crop acre as the basis in such comparisons as the costs of power and labor. However, so far as farm size affects the cost of power per hour, or, still more, per crop acre, it is primarily not the number of crop acres in the farm, but the amount of power work used, that matters. When the farmer has much power work to do, he usually is able to utilize the available sources of power more intensively than a farmer with little power work. In a farm with a considerable amount of power work, it is also easier to have all implements adjusted to the power of the tractors, thus insuring their more efficient utilization. Only the size of the fields depends on the number of acres, and not on the amount of work done per acre. Under these conditions, it seems advisable, when using the horse-hour equivalent as the basis for the computations of the cost of power, to employ it also, in power studies, as the measure for farm size. The crop acre is a general measure of the farm size, and as such necessarily lacks precision. An examination of the subject frequently compels one to adopt specific measures for specific problems. The most important of these measures to replace the crop acre in farm studies proved to be the productive-man unit, as measured in hours or days, worked by an adult man. For power studies, the horse-hour equivalent seems to be the adequate specific measure. 10 It is worth noting that Washburn and Scudder, in their study on Cost of Using Horses, Tractors and Combines on Wheat Farms in Sherman County, Oregon—this is one of the earlier studies dealing with tractors—provided in Table 24 (p. 25) very detailed data for non-tractor farms of a size comparable with the tractor farms for which data were supplied.

EFFECT

OF

FARM

SIZE

ON

COST

209

AVERAGES OF C O S T OF P O W E R FOR F A R M G R O U P S W I T H D I F F E R E N T T Y P E S OF P O W E R

The next, and in many respects the most direct, conclusion to be drawn from the fact that the size of farms has a great effect on the cost of power per crop acre is the following: If type-of-power groups of farms of unequal average sizes are compared, and the cost of power per crop acre on these farm groups shows variations, these variations may or may not be in part due to differences in the type of power; but always, and to a large extent, they are caused by differences in the size of the compared farm groups. If no variation in the cost of power is revealed by the figures, there is a strong probability that the effects of the two causes have offset each other. The average cost of all power per crop acre on Corn Belt farms was computed in the Corn Belt study 11 at $4.70 for general-purpose tractor farms, and at $5.32 for horse farms. However, no general-purpose tractor farm had less than 100 acres in crops; the average for all general-purpose tractor farms included in the study was 196 crop acres. On the other hand, out of the 343 horse farms, 123 had less than 100 crop acres; the average for all horse farms was only 137 crop acres. If, then, the horse farms which have less than 100 crop acres are excluded from the totals for horse farms, the average cost of all power on these farms goes down to $4.91 per crop acre. By this simple operation, two-thirds of the apparent difference in the cost of power between the two groups is slashed off. Yet, the average number of crop acres per horse farm still remains smaller than the average for the general-purpose tractor farms (173 crop acres, as against 196). If so many horse farms with from 100 to 139 crop acres are excluded that the average for all horse farms is raised to 196 acres, the average cost of power on horse farms is further reduced to $4.73, or practically to the average cost on farms with general-purpose tractors. 12 Thus 11 Reynoldson et al., Utilization and Cost of Power on Corn Belt Farms, pp. 45, 48. "The average acreage and the average cost of power per crop acre for the group of horse farms with from 100 to 139 acres has been used in this computation. If the smallest farms of this size group were used, the average cost of power per crop acre on horse farms would probably be less than on general-purpose tractor farms of comparable size.

210 E F F E C T OF FARM SIZE ON COST the difference in the cost of power between general-purpose tractor and horse farms, computed on a per-crop-acre basis, was entirely due to the effect of the differences in the size of the farms (see Chart 15). This example is not an isolated one. The average size of horse farms is less than that of the tractor farms, in every C H A R T IS T H E E F F E C T OF E L I M I N A T I N G T H E D I F F E R E N C E S I N T H E SIZE OF F A R M S O N T H E COST OF POWER P E R CROP ACRE, O N G E N E R A L - P U R P O S E TRACTOR F A R M S A N D ON H O R S E FARMS, C O R N BELT, 1929 D O L L A R S PER CROP ACRE

2

3

4

SIZE OF FARMS DIFFERENT SIZE OF FARMS EOUAl General-purpose tractor farms

ZZ2X Horse farms

The data plotted in the two upper bars are from Reynoldson et al., Utilization and Cost of Power on Corn Belt Farms. The general-purpose tractor farms had, on an average, 196 crop acres, while the horse farms averaged only 137 crop acres. This difference was eliminated by a procedure indicated in the text (p. 209). The cost of power per crop acre, which, on the basis of the original data, is considerably smaller on general-purpose tractor farms than on horse farms, becomes equal on the t w o type-of-power groups of farms when the effect of the size of farms is eliminated.

study known to the present writer. Moreover, the difference in the average size is commonly so large that comparison of the data is definitely precluded. When the average size of all farms belonging to different type-of-power groups is not equal and the investigator has not made up his mind to drop these averages, it is well to keep in mind that for comparing the cost of power of various type-ofpower groups, these averages are by far inferior to the averages by size groups. For example, the average size of all investigated tractor and horse farms may be 250 and 150 crop acres respectively, and the data on the cost of power, therefore, may

E F F E C T OF FARM SIZE ON COST 211 be incomparable; yet the data for the groups with from 150 to 199, or from 200 to 249, crop acres may permit fairly reliable conclusions. Investigators, however, do not always follow this course.13 Averages for all farms of each type-of-power group often are emphasized, with averages by size groups receiving only secondary attention. Summaries which reveal what the authors themselves think to be the most important of their findings, and which are the only part read by many, frequently deal only with the averages for all farms belonging to the same type-of-power group, with the averages by size groups entirely disregarded. Moreover, the data by size groups are not always provided in a form which would enable the reader himself to make the necessary comparisons. For this purpose all data included in the report should be by size groups. Yet it is a rather common practice to classify only a part of the data according to type of power as well as by farm size. In the Corn Belt study, for example, only tables on the annual use of various kinds of power and their cost, as well as data on the cost of the drawbar power used in growing and harvesting crops, are classified according to farm size. Data on the cost of operating tractors and horses per hour are provided by types of power only. Computations of labor and power used and the cost per acre for growing and harvesting various crops (Tables 21-24 of the study) are likewise averages for all farms, regardless of size. Yet it should be borne in mind that in many other investigations the grouping of data by size of farms is not carried so far as in the Corn Belt study. The situation is particularly unsatisfactory if no figures by size groups are presented, the only data made available being the averages for whole type-of-power groups of farms of unequal average size. In brief, an indispensable requirement for proper comparisons of the cost of power on tractor and horse farms is that the average size, both of tractor and horse farms, be the same. This primarily pertains to computations of the cost of power "Johnston and Wills, authors of the Illinois study, go still further than this cautious recommendation. N o averages at all are computed for w h o l e t y p e - o f power groups, the only averages given being those by size groups for each typeof-power group. It is hoped that future investigators will follow the example set in the Illinois study.

212 E F F E C T OF FARM SIZE ON COST per crop acre. Yet it is valid also for computations of the cost per horse-hour equivalent, because the cost per horse-hour equivalent also is affected by the size of farms. The large difference frequently observed in the average size of investigated tractor farms, as compared with horse farms, is the natural consequence of the fact that larger farms are more prone to use tractors than small farms. The necessity of having comparable averages, therefore, ought to be considered before the collection of data has commenced. If this is not done, it will be necessary later to omit a considerable part of the original material, so far as it is not needed for purposes other than a comparison of the cost of power on different type-ofpower farms.14 It would be premature to conclude that, by complying with the requirement of an equal average size for farms in each of the various type-of-power groups, the comparableness of the cost of power on farms with different types of power would be definitely ensured. Further implications should be taken into consideration. A comparison of average costs of power on different type-of-power groups, of the same average size, discloses different results, depending on the level at which the comparison is being made. Moreover, even the variations in the dispersion about the same averages may be significant. As shown in Chart 13, the rate at which the cost of tractor and horse power per time unit declines slow down as the amount of power work increases, until eventually the curves become horizontal. A similar situation prevails with regard to the amount of power per crop acre, and therefore, with double force, with regard to the cost of power per crop acre. This specific form of the curves for the cost of power on farms of different sizes would not affect comparisons of the cost of power on different type-of-power farms, were the shape of all curves similar.15 This occurs but rarely, however. The cost of " I f the data were collected for the specific purpose of comparisons of the cost of different types of power, the actual frequency of tractor and horse farms of different sizes would not be reflected in the selected sample. Most investigators, however, would prefer to gather data which may be considered representative for each type of power. Then it would be a matter of arranging the collected data for each purpose separately, instead of using the same arrangement for all purposes. " T h e similarity would have to be of somewhat different kinds, depending on whether the cost of power on different type-of-power farms should be

E F F E C T OF FARM SIZE ON COST 213 power per crop acre on horse farms is likely to decline more slowly with the increase in the size of farms than it does on tractor farms; or, in other words, the curve for the cost of horse power may be expected to be less steep than that for tractor power (see Chart 13). According to the data of the Corn Belt study, 16 the cost of power per crop acre on ordinary two-plow tractor farms with from 100 to 139 acres in crops averaged 59.4 percent higher than on similar farms with 300 and more acres; on horse farms of the same sizes the difference was only 37.7 percent. After unweighted averages of the weighted averages of groups with from 100 to 139 and from 140 to 179 crop acres, on one hand, and with from 260 to 299 and with 300 and over crop acres, on the other hand, are computed,17 the cost of power on ordinary two-plow tractor farms with 260 and more crop acres is 48.0 percent lower than on similar farms with from 100 to 179 acres; while the difference is only 29.5 percent for horse farms of the same size groups. This flatness of the horse curve, as compared with that of the tractor curve,18 evidently indicates a result more favorable to the tractor, or less unfavorable, as the size of farms increases. The rather widespread opinion that horses have an invincible position on small farms and that the competitive power of tractors on farms of different sizes differs greatly needs to be considerably modified.19 Some of the figures of the Illinois comparable at different farm size levels in absolute figures or on a percentage basis. * Reynoldson et al., op. cit., pp. 43 and 47. " Reducing the number of size groups seems advisable, since some of the original size groups evidently contain irregularities, resulting from too small a sample. It seemed, however, unnecessary to weight the averages, as is commonly done, using as weights the number and acreage of the farms in each size group. The value of this procedure is rather doubtful, because the probability is remote that the size distribution of the farms covered will correspond with the distribution of farms in the investigated area, and this would be the only justification for the use of those weights. " The curve for horse farms is also likely to cease to decline at a lower size level than is the case with tractor farms. u There are rarely more severe contradictions met with than that, on one hand, the great superiority of horses over tractors on small farms frequently is accepted as a fact for which proofs are superfluous; and that, on the other hand, tractor farms, which are too small even for a moderately sized team, are included in the computations of average costs of power that are destined to provide the basis for a general decision as to the profitableness of tractors.

214 E F F E C T OF FARM SIZE ON COST study, presented in Charts 8 and 9 (see pp. 136 and 140), indicate that tractors on small farms are even relatively more advantageous than on larger farms. This is undoubtedly incorrect and points towards the inadequacy of the data on the total cost of power, labor, and machinery, used in that study, for comparisons of different sources of power (see page 139). Other data are not so favorable for small farms as the data of the Illinois study, but they, too, show that under specific conditions or combinations of conditions, such as high feed prices, high wages, and the like, tractors may be used on small farms to advantage, although the profit is smaller than on larger farms. The favorable showing made by tractors on small Illinois farms was primarily the result of the large saving in the cost of labor on small farms using tractors. On the basis of the cost of horses and machinery, without the cost of labor, the situation on the investigated Illinois farms was more favorable for tractor use on large farms. Not infrequently the expense for power alone on small farms actually increases after a shift to tractor power. Tractor power should be very cheap, as compared with horse power, in order to enable it to compete successfully with horse power on small farms on a purely costoj-power basis. The notion that tractors on small farms are useful for power work which can also be done by horses is frequently due to some circumstance lying outside the field of direct competition between tractor and horse power, rather than to a direct saving on the cost of power. Many small farmers keep tractors because they have much belt work to do, and the hired power for belt work is not available when needed. Or a man can drive a tractor, but is unable to drive horses. Sometimes tractors make possible rotations which cannot be attained with horses. The most important factor usually is the saving in labor. Hence figures on the cost of power on small farms taken alone will usually show a loss, either real or fictitious,20 which may not be encountered on farms of a size more suitable for tractor use. It may, therefore, seem inadvisable to include data for farms under some minimum size, in the averages used in comparing the cost of tractor and horse power. It is evident, furthermore, that not only may comparisons "Fictitious, because some of the advantages of tractors elude statistical expression.

E F F E C T OF FARM SIZE ON COST 215 between tractor and horse farms be impaired by including too small farms in the computations of the averages, but that the same is true also for comparisons of farms with different-sized and differently used tractors." The larger the tractor and the less it is used per crop acre, the larger must be the minimum size of farms included in the computations of averages Even with the data for farms under certain minimum sizes excluded from the averages, the findings are likely to be the more favorable for tractors, the higher the average size of farms at which the comparison is made. For example, if unweighted averages are computed of the weighted average costs of power in the six size groups with 100 and more crop acres, for horse and general-purpose tractor farms considered in the Corn Belt study, the cost of all power per crop acre in 1929 on horse farms was 1.3 percent higher than on tractor farms. With the minimum size increased to 140 crop acres and the consequent increase in the average farm size, the difference in the cost becomes 4.5 percent, to the disadvantage of the horse farms. The statement made in the preceding paragraph is also valid for farms with tractors of different sizes. Similarly, the adverse effect of a reduction in the average level of farm sizes is smaller, in most cases, for farms using tractors as the main source of power than for farms using tractors as the subsidiary source of power. This also can be demonstrated by the figures of the Corn Belt study. Of the three type-of-power groups with tractors, the farms with three-plow tractors showed the greatest difference in the cost of power per crop acre between farms "Apart from the greater farm size necessary for the profitable operation of the larger tractors as compared with smaller tractors, the computations are often biased against larger tractors by the fact that advantages, difficult to calculate in figures (timeliness of field work and independence from hired belt power), are usually greater in the case of larger tractors. " N7ote that we are speaking only of excluding the farms of under a certain size from the general averages. It is not supposed that farms under minimum size would be left entirely without consideration. The use of tractors on small farmi should be studied, even if they were always operated at a loss, for it is very important to know the competitive power of tractors, not only under conditions more or less suitable for the use of tractors, but also under circumstances distinctly disadvantageous. Since the competitive power of tractors on small farms is considerably greater than is usually believed, there is still less reason to disregard such farms in power studies. Yet the peculiarities inherent in the nature of the competition of tractors and horses on small farms probibly make it preferable to treat those farms separately. A somewhat more techrical discussion of the problem of minimum sizes is presented on pp. 218-20.

216 E F F E C T OF FARM SIZE ON COST with from 180 to 259 acres and with 260 crop acres and more it amounted to $2.12. The smallest difference was on farms with two-plow general-purpose tractors ($0.27). 23 Thus the competitive position of the tractors of large size and of those adapted to fewer operations improves as the size of farms increases, as compared with tractors of small size and with those adapted to a greater number of operations. Since the rate of the decline in the cost of power diminishes as the size of the farms increases, even the dispersion of the TABLE 18 COST OF ALL POWER

ON GENERAL-PURPOSE C O R N B E L T , 1929°

Size group in crop acres to 1 3 9 to 1 7 9 to 2 1 9 to 2 5 9 to 2 9 9 300 and over Weighted Average Unweighted Average of the 1 Weighted Group Averages/ 100 140 180 220 260

TRACTOR

FARMS,

Cost of power per crop acre $6.31 5.16 4.52 4.06 4.59 3.45 4.70 $4.68

" Reynoldson et al., Utilization and Cost of Power on Corn Belt Farms. The averages by size groups are weighted.

individual farms about the average size is likely to affect the average cost of power on these farms. An average cost of power for farms with an average size of 200 crop acres and a range of, say, 100 to 300 crop acres may be expected to be somewhat higher than a similar average for farms with an average size of 200 crop acres and a range of from 150 to 250 crop acres. This can be illustrated by the data of the Corn Belt study for general-purpose tractor farms (Table 18). While the weighted average size of all general-purpose tractor farms is 196 crop acres and the weighted average cost of power on them is $4.70 per crop acre, the weighted average " General-purpose tractors in the Corn Belt are used both as the main and the auxiliary source of power, while ordinary tractors can be used only for auxiliary purposes (see pp. 4-9).

E F F E C T OF FARM SIZE ON COST 217 cost of power is only $4.52 on farms with from 180 to 219 crop acres and averaging 194 crop acres. The unweighted averages of weighted averages of individual size groups, which probably are more representative than the weighted averages, show still greater divergencies. The unweighted average of the weightedaverage costs for all six groups is $4.68 per crop acre. It is only $4.29 for the unweighted average of the weighted averages of the two intermediate size groups (farms with from 180 to 219, and with from 220 to 259, crop acres).2* The curve for the cost of power per crop acre on tractor farms usually is steeper than a similar curve for horse farms. Hence with the type of curves involved, a comparison of the average cost of power on horse and tractor farms of a certain size is likely to be more favorable for tractors, the smaller the range of dispersion of individual farms about the same average. It is obvious from the above reasoning that the size of farms greatly affects the cost of power per crop acre, and that it is immensely important to guard against allowing this effect to interfere with conclusions on the competitive position of different types of power. For this purpose, first of all, farms of less than a certain minimum size should not be used in computing averages. Moreover, the averages ought to be broken up into subaverages, by providing as many groups by farm size as compliance with other requirements permits. If only a few size groups can be formed, provision ought to be made for having the average size of farms in each size group equal for all type-of-power groups, or some adjustment for the deviations may become necessary. When findings of studies are used, or findings of different studies compared, attention ought to be given to the size of farms from which the findings have been derived. Finally, we have to consider the changes which should be made in the above conclusions if the horse-hour equivalent should be substituted for the crop acre in its various functions. We know that when, in the computations of the cost of power, " The figure for the group of farms with from 220 to 259 crop acres, used in the comparison, lies below the expected value, but the expected value too, is substantially less than $4.68.

218 E F F E C T OF FARM SIZE ON COST the crop acre is replaced by the horse-hour equivalent, the variations in the amount of power used per crop acre are eliminated; but the variations in the cost per hour, whatever the reason, remain untouched. Hence variations in the cost per hour caused by differences in the size of farms are also present. When the cost of different types of power is compared, precautions ought to be taken that both the variations in the amount of power per crop acre and in the cost of power per hour, caused by the variations in the size of farms, do not impair the results of those comparisons. Since, by using the horse-hour equivalent, only the variations in the amount of power per crop acre are eliminated, the recommendations presented above should be carefully adhered to even in computations made on the basis of horse-hour equivalents. The extent of the harm which may result from disregarding them, or not following them strictly, it is true, is considerably less than when the cost of power is computed per crop acre. But using in the computations of the cost of power on different type-of-power farms the horse-hour equivalent as the measure of farm size, without using it at the same time as the basis in computations of the cost of power, may easily lead to incorrect inferences. In the grouping on the basis of crop acres, the small size groups include a substantial portion of farms which use a considerable amount of power. If the grouping is made on the basis of horse-hour equivalents, these farms shift into higher size groups, with the result that the average cost of power per hour in the smallest size groups is increased. Thus the curves of the cost of power per unit are considerably steeper, if the grouping by farm size is made on the basis of horse-hour equivalents, rather than on the basis of crop acres; and this steepness of the curves is the factor which should be prevented from affecting conclusions. Hence it is probably better to abstain from accepting the recommendations on measuring the size of farms in horse-hour equivalents, if the recommendations about the grouping of farms by size cannot be followed. M I N I M U M SIZES

It has been shown on pages 213-15 that for proper comparisons of the costs of power on farms with different types of

E F F E C T OF FARM SIZE ON COST 219 power, farms under certain minimum sizes should not be used in the computations of the average costs.25 The sizes to be excluded depend in the first instance upon the size of tractor and upon the kind of crops grown. It is also very significant whether the tractor is used as the main, or as the subsidiary, source of power. If horses which are kept on the farm only for peaks of power work are replaced by tractors, the work formerly performed by horses can be accomplished by the tractor in a relatively small number of hours. In other words, a tractor used as a subsidiary source of power for peak work replaces more horses with the same amount of annual work than it would replace in work more regularly distributed over the year. Hence the tractor used as a subsidiary source of power is able to bear a higher per-hour cost than a tractor used as the main source of power. The difference in the amount of work per acre performed by tractors used as the main source of power and that of tractors employed as the subsidiary power, however, is so large in most cases that, in spite of the ability of tractors used as the subsidiary source of power to bear higher expenses per hour of operation, the minimum acreage for these tractors will usually be considerably larger than for tractors used as the main source of power. A tractor with about 11 adjusted horsepower, used on Corn Belt farms as the auxiliary source of power, is usually operated about two hours per crop acre. For tractors with about 16.5 adjusted horsepower the figure is not quite 1.5 hours per crop acre. For tractors with about 11 adjusted horsepower, used as the main source of power, the figure is probably equal to about 3.0, or somewhat more.26 The minimum size of a Corn Belt farm, large enough to use a tractor only during rush periods, * The proposal to exclude farms of less than a certain size from the averages for all farms of the respective t y p e - o f - p o w e r groups should not be so understood that different type-of-power groups, when compared, would have different minimum sizes. If, for example, the cost of power on farms with tractors with 16.5 adjusted horsepower has to be compared with the cost on farms w i t h smaller tractors or with horses, the minimum size for all t y p e - o f - p o w e r groups ought to be the one believed appropriate for the farms with the larger tractors. " When tractors do all the work, apart from planting and part of the cultivating. 3.9 hours of work of a general-purpose tractor (probably t w o - p l o w tractor) are spent per acre of corn harvested by hand, according to the Missouri study (Smith and Jones, op. cit., Table 16). If the corn is picked b y a picker, the number of hours of tractor work per acre of c o m rises to nearly S.

220 E F F E C T OF FARM SIZE ON COST would probably be about 1.5 times the minimum size of a farm that uses the same tractor as the main source of power. It seems reasonable to treat separately, as farms of less than the minimum size, those Corn Belt farms with less than 100 crop acre which use general-purpose tractors with steel wheels, with about 11 adjusted horsepower, as the main source of power. About ISO, and about 200, crop acres would probably represent the minimum sizes for Corn Belt farms using tractors with about 11 and 16.5 adjusted horsepower respectively, as the subsidiary source of power. If, instead of the crop acre, the horse-hour equivalent should be used in power studies as the measure of farm size, about 2,500 horse-hour equivalents of yearly drawbar field work might perhaps be an adequate amount to use as the minimum size for farms operating general-purpose tractors with about 11 adjusted horsepower, as the main source of power. The corresponding minimum yearly power work for farms operating tractors with 11.0 and 16.5 adjusted horsepower as the subsidiary source of power would be about 3,500 and 4,500 horsehour equivalents respectively. GROUPING OF FARMS BY SIZE

There is not much similarity in the manner of grouping farms according to size. In the study Utilization and Cost of Power on Corn Belt Farms, Reynoldson et al. presented 8 groups. The class interval was 40 acres, with the exception of the lowest and highest groups. The upper open-end group (300 and more crop acres) is particularly indefinite; the average crop acreage in this size group varies from 339 crop acres on ordinary horse farms to 380 crop acres on ordinary threeplow tractor farms. Johnston and Wills, in the Illinois study, also distinguished 8 groups for each type of power. The class interval was likewise 40 acres, except for the largest size group. Schwantes and Pond, in the Minnesota study, provided 6 groups, with a class interval of 100 acres, while Fain et al., in the Georgian study, had only 3 size groups: farms with less than 100 crop acres, farms with from 100 to 300 crop acres, and farms with 300 crop acres and over. It has been shown (pp. 216-17) that the dispersion of the

E F F E C T OF FARM SIZE ON COST 221 individual cases around their average should be as small as possible. On the other hand, figures for individual size groups, even in studies with the largest number of investigated farms, are not always free from contingencies. For this reason it seemed necessary, when dealing with the 6 size groups of the Corn Belt study, with 100 and more crop acres, to combine each two, thus reducing the whole to 3 groups (p. 213). A glance at Charts 8 and 9 indicates that even in the Illinois study, which includes an unusually large number of farms, the figures for individual size groups reveal variations of undoubtedly fortuitous character; a reduction of the number of size groups from 8 to 4 in that study would considerably improve the picture. The fortuitous nature of many results is not surprising, when the number of farms in the individual groups is considered. The usually rather limited total number of farms covered by studies results in the individual size groups becoming dangerously small, even if the number of groups is restricted. The Illinois study covered 342 horse farms, in 1930. Yet in the groups with from 240 to 279, from 280 to 319, and 320 and more, crop acres, only 8, 6, and 3 farms, respectively, were included. The smallest size group of farms with general-purpose tractors consisted of but 4 farms in 1930, and of only 2 in 1931. The distribution of farms by size in the Corn Belt study27 was somewhat more even. Yet there were only 10 ordinary horse farms with from 260 to 299 crop acres, and only 8 and 7 general-purpose tractor farms with from 220 to 259, and with 300 and more, crop acres respectively, not to speak of big-team-hitch farms, for which the number of farms in the individual size groups varied from 3 to 8 farms only. A small number of farms in a size group is particularly dangerous if the area covered by the investigation is not uniform. It cannot be expected that figures for size groups will be comparable, if, for instance, 11 different areas are included in a study, as is the case with the Corn Belt study, and some size groups consist of 8 farms or less. Before subdivision in size groups is decided upon, a check should be made to ascertain whether the resulting number of farms in each group will pro" Reynoldson et ai., op. cit., Table 4, and others.

Ill E F F E C T OF FARM SIZE ON COST vide sufficient insurance against contingent influences. For some conclusions, the data might stand a very detailed distribution by size. For other computations, only a few size groups may be admissible, and in some cases a distribution by size should not be used at all. Generally speaking, no more size groups should be established for each computation than can meet the requirements of real comparableness. The fact should not be overlooked, moreover, that the figures by size groups have to be usable for comparisons between different type-of-power groups, as well as vertically in the series for each type-of-power group. If the number of farms in some of the size groups is small, this requirement will also not be fulfilled. Thus, owing to the peculiar form of the curves for the cost of power, investigators are faced with the alternative of pitfalls arising from having too many size groups and pitfalls which originate from having too few. In each case it will be necessary to determine which is the lesser evil. The utilization of the horse-hour equivalent as the basis for computing the cost of power helps in this task by eliminating that part of the variations in the cost of power on farms of different sizes which result from variations in the amount of power used per crop acre. But the task remains difficult. In many cases it may be found preferable to abstain from the study altogether rather than to base it on an absolutely insufficient sample. More frequently the solution may lie in confining general studies on farm power to a few farm sizes typical for the region, leaving less typical sizes for special investigations. EFFECT OF SIZE OF FARMS ON OPERATING COSTS OTHER T H A N

POWER

So far as the effect of the size of farms is concerned, the situation regarding labor and machinery is similar to that of power. The decline in the amount of labor used per crop acre on large farms, as compared with that on small farms, is even greater than the decline in the amount of power. According to the Illinois study,28 labor available on farms with 300 acres "Johnston and Wills, op. cit., p. 312.

E F F E C T OF FARM SIZE ON COST 223 in crops was only twice as large as that available on farms with 100 crop acres. As opposed to the cost of power, the cost of labor per hour does not decline on farms of larger size. If there is some variation, it is in the opposite direction, the cost of labor per hour being higher on large farms than on small farms. In spite of this, the cost of labor per crop acre declines sensibly, as the size of farms increases, because the decline in the amount of labor used per crop acre greatly exceeds the increase in hourly wages, if any. Large-sized machinery is relatively cheaper than small machines. For machinery cost per crop acre, we have, therefore, on larger farms, the same cumulative effect of the reduction in the amount used per crop acre and in the cost per unit which was shown for the cost of power per crop acre. Thus all considerations pertaining to the necessity of guarding against the effect of the farm size on the cost of power, on different type-of-power farms, apply as well to the cost of labor and machinery per crop acre.

IX SELECTING THE AREA in power studies arising from combining into averages data for areas varying as to soil, topography, and other physical conditions are so widely recognized that it is not necessary to dwell at greater length upon this subject. Both important items of the cost of horse power, feed and horses, vary widely in value from region to region. The variations in the prices of the principal items of the cost of tractor power, although much less than corresponding items in the case of horse power, also are wide. Moreover, the variations between the prices of horses, feed, and so forth on one side, and the prices of tractors, fuel, and so forth on the other are frequently directly opposed. This divergence alone would be sufficient to necessitate a careful selection of similar areas. There is, however, another reason in favor of such a procedure, which is not quite so obvious but perhaps even more important. It has been shown (Chapter III, pp. 50-51) that equal costs of power may have rather divergent meanings, depending on whether a certain type of power is used as the exclusive, principal, or occasional source of power. The same is true for farms with different organizations. A highly specialized farm business is usually able to bear greater expense than a general farm business, the principal advantage of which is cheap unit costs of power and labor. The nature of the costs of tractor and horse power, however, is such as to tend to make tractor power more profitable on specialized farms than on general farms. Since less power work usually is done per crop acre on specialized farms, the cost of power per crop acre tends to be low. Yet it tends to be relatively high on a per-unit-of-power basis, owing to the smaller number of hours that the power is used during the year. Since the cost of tractor work per hour varies with the variations in the length of the annual use per tractor considerably less than does the cost of horse work per horse hour, the tractor is a particularly appropriate source of T H E DANGERS

SELECTING THE AREA 225 power on specialized farms, where the number of hours that power is used during the year is small. Ceteris paribus, therefore, the more specialized the production of a country, region, area, or farm, the more profitable are tractors. Once introduced, tractors stimulate further specialization. On the contrary, horses, the unit cost of power of which is much greater where the annual utilization of power is small, are more appropriate for general farming. This is especially true when we remember that general farming means the production of crops with divergent seasonal distribution of power requirements, as well as livestock enterprises which call for the use of power during a considerable portion of the year. By way of illustration, let us take two farms with different degrees of specialization. Let us assume that these two farms have a total of 3,000 horse-hour equivalents of power work per year. Each can perform the work with similar tractors. The cost of power would be about equal for both, if tractors were used. If horses are used, however, one of the farms would need 5 horses working 600 hours each, while the other farm could do with 3 horses used 1,000 hours each. The cost of keeping 3 horses worked 1,000 hours annually is much smaller than the cost of keeping 5 horses working 600 hours each. Thus it is possible that a tractor might be profitable on one farm and unprofitable on another, although the prices of feed, tractors, and fuel were equal on both. The saving of labor is frequently the decisive factor in determining whether the tractor is profitable or unprofitable. Combining areas with different types of farming involves the risk that farms with relatively small power requirements, but large labor requirements, may be included in groups with farms on which both power and labor requirements are small. While the latter may find trouble in gainfully employing the labor saved by the use of tractors, the farms with large labor requirements will experience no such difficulty. A rigid fulfillment of the recommendations presented in other parts of this study (grouping of farms according to type, size, number, and function of the operated tractors; and basing comparisons of the cost of power on the horse-hour equivalent) would eliminate to some extent the disadvantages of

226 SELECTING T H E AREA combining farms operated under different economic conditions. It is particularly significant that by utilizing the horse-hour equivalent as the basis for computing the cost of power the risk of comparing cost of power on farms which apply unequal amounts of power per crop acre would be eliminated. Yet a thorough checking of the investigated areas with regard to their uniformity is indispensable not only for all investigated farms using the same type of power and taken together, but for each size group of farms separately. It is of particular significance, when selecting the area, to guard against combining in one group, areas in which the farms, on an average, operate their horses, say, 1,200 hours, with regions where the average number of hours per horse is, say, 800. The most rigid selection of an area sometimes will not insure complete uniformity of farm organization. Farms within the selected area which diverge considerably from the general type simply must be excluded from the survey. As already stated, the necessity of choosing areas with the greatest possible uniformity is widely recognized. Gilbert, in the New York study, presents his data for four specialized areas, each consisting at most of two counties, and some of only part of a county. The Missouri and the South Dakota studies also covered only one county each. The nearly 1,600 farms included in the Illinois study are concentrated in the central part of the state. Not satisfied with this, Johnston and Wills1 selected exclusively all-tillable farms in east-central Illinois, for their study of matched records, mentioned above. The data of the Indiana study also pertain only to the central part of the state. The Corn Belt study comprises five states. Yet the investigated farms were selected only from eleven relatively small areas,2 consisting of from one to two counties each. In each area ordinary horse farms and farms with ordinary tractors have been selected. Farms with general-purpose tractors were selected from ten out of the eleven areas. Unlike Gilbert and some other writers, the authors of the Corn Belt study did not provide data for each area separately. The variations in type of farm1 Op. cit., p. 313. ' S e e Chart 1, p. 2, of the study on the Cost and Utilization of Power on Com Belt Farms by Reynoldson et al.

SELECTING T H E AREA 227 ing have hardly impaired the comparableness of averages for tractor farms and for ordinary horse farms, so far as the averages are for the type-of-power groups as a whole. Some doubt may exist as to whether the difference in type of farming of the various areas did not affect the comparableness of the data pertaining to farms of the same size group but with different types of power, as well as that of farm groups of various sizes but with the same type of power.3 This circumstance is rather important, because some averages, computed for all investigated farms of each type of power, are not very significant, and an analysis of the data by size groups cannot be dispensed with, even if the averages for all farms meet all requirements of proper statistical data. The Minnesota study constitutes a sharp deviation from the standard. It combines two typical Corn Belt areas, designated as "Southwest" and "Southeast," with an area belonging to the Spring Wheat Belt and designated as "Northwest." The extent to which the first two areas differed from the third is apparent from the fact that the farms in the Southeast and the Southwest had, on an average, 146 and 236 acres in crops, while those in the Northwest averaged 425 acres. In the Southeast and the Southwest areas, 31 percent and 42 percent of the crop acreage was in corn and potatoes, while in the Northwest area only 6 percent of the crop acreage was devoted to these crops. In the Southeast and the Southwest areas 49 percent and 54 percent of the tractors were of the two-plow size, as against only 28 percent in the Northwest area. The annual use of tractors was 311, 398, and 522 hours per tractor, respectively. These figures make it clear that the data on the cost of power per hour, and for the cost of individual operations (Tables 16-19), which are made without regard to the sections to which the data pertain, cannot possess the significance they would have otherwise. The averages for such developments as changes in the size of farms and the number of acres cropped, increases in productive livestock and labor supply, and so forth, likewise lose much of their value. The farms in the Northwest had prob* The data on big-team-hitch farms were selected only from five areas out of a total of eleven. One is not sure that even averages for all farms of this type of power are comparable with averages for the other type-of-power groups.

228

SELECTING T H E AREA

ably much more opportunity to increase the crop acreage and to reduce the labor supply, or both, than farms in the two other sections, where there was more opportunity for increasing productive livestock.

X SUMMARY T o DETERMINE whether tractors or horses are the cheaper source of farm power is a much more difficult task than is frequently assumed. When the difference between the cost of tractor and horse power is moderate and the cost of power constitutes only a relatively small part of total operating costs, it may even prove impossible to reach reliable conclusions. Much more refined methods, in any case, should be applied than those usually employed in power studies. GROUPING BY TYPE OF POWER. A correct study of farm use of tractors requires, first of all, an adequate grouping of the investigated tractors, and of the farms using them, by type of power. Five types of tractors must be distinguished: (1) ordinary tractors with steel wheels, (2) general purpose tractors with steel wheels, (3) rubber-tired ordinary tractors, (4) rubbertired general-purpose tractors, and (5) crawlers. Each of these types has such distinct peculiarities that failure to segregate them may endanger the findings. In addition to operations for which ordinary tractors are adapted, general-purpose tractors are used for cultivating row crops. The broader scope of operations assigns to them a role which differs considerably from that of ordinary tractors in regions where row crops represent a substantial proportion of the total crops. Rubber-tired tractors are at a disadvantage on wet ground, as compared with tractors with steel wheels. In normal conditions, however, they seem to be more efficient, particularly when operated at high speed. Moreover, rubber-tired tractors can be used for hauling on the road. Crawlers are more durable than tractors with steel wheels, and more efficient in utilizing the power developed by the engine, but their first cost is greater and they require more repairs. The size of farm tractors varies widely from the equivalent of 4-5 horses to the equivalent of 30-40 horses. Grouping the investigated farms by the size of their tractors, or eliminating

230 SUMMARY from the tabulations farms with tractors under and above certain narrow size limits, is therefore indispensable. The grouping or the eliminating, however, requires a constant and definite measure of power. Neither of the two commonly employed units, that is, the number of plows a certain tractor draws or is supposed to draw, and the rated horsepower (H.P.), in the form in which they are used in power studies, is satisfactory. The number of plows a tractor can draw depends not only on the power of its engine, but to a great extent also on such a variable factor as the speed of the tractor. Moreover, a number of factors which have nothing to do with the power of tractors (cohesion of the soil, width of the plow, depth of plowing, and topography) affect the number of plows a tractor can pull. The result is great variability in the amount of power required and provided per plow, in tractors of the same type but constructed in different years (the speed of tractors has been increased greatly since their introduction), in tractors of different types, and, to a lesser extent, even in tractors of the same type constructed at the same time. The number of plows actually used with tractors on farms is a very vague unit of measurement of tractor power. Even the most elementary rules of proper statistical analysis cannot be applied, if the data are arranged on the basis of this measure. Considerable overlapping, for instance, is inevitable. The situation is improved somewhat if the investigators themselves determine the number of plows that can be drawn by the tractors included in their studies, irrespective of how these tractors are used on the investigated farms. The plow, however, still remains a very indefinite and variable unit of measurement. The same is true for the plow as the class interval in the grouping of tractors by size. Usually it is not even known whether "two-plow," "three-plow," and so forth, used as the designations of the size groups of tractors, are the mid points of the respective groups, their low limits, or some point in between. Since the plow is a large unit of measurement, being equal to 100, SO, and 33.3 percent of the power of the three most used tractor sizes, this vagueness and variability not only prevents comparisons of such findings as are simultaneously obtained in different states, and at intervals in the same states, but even greatly reduces the value of the findings of each separate study.

231 SUMMARY The rated horsepower, as established by the manufacturers or by the official tractor tests in Nebraska, at manufacturers' ratings, were so uncomparable that no advantage could be gained from using them instead of the plow as the measure of tractor power. Since 1930, however, the rated horsepower tests have been conducted at the highest permissible ratings recommended by the Tractor Rating Code of the A. S. A. E. and S. A. E. (85 percent of the corrected maximum belt power and 75 percent of the corrected maximum drawbar power). After this change, the rated power provides an entirely comparable basis for all tractors, with respect to belt work. As regards the more important drawbar power, the highest permissible ratings are comparable only for tractors of similar construction (tractors with steel wheels, rubber-tired tractors, crawlers). The portion of the maximum drawbar power of crawlers which can be utilized continuously under average farm conditions is greater than that of tractors with steel wheels. Hence using the same percentage in establishing the rated drawbar power of different types of tractors, as is recommended by the rating code of the A. S. A. E. and S. A. E., is inadequate. It is proposed, therefore, to use as the measure of tractor power the adjusted drawbar horsepower, which for crawlers not used for belt work coincides with the highest permissible drawbar ratings as established in Nebraska, while for tractors with steel wheels these ratings are reduced by 20 percent. The adjusted drawbar horsepower not only has the advantage of making the drawbar power of tractors of different types comparable, but for tractors with steel wheels there is the further advantage that the adjusted horsepower does not exceed that portion of the power of these tractors which is used in actual field work by such a large margin as do the highest permissible ratings of the Tractor Code. The percentage recommended for the reduction of the highest permissible ratings is preliminary. Even a preliminary estimate of the relationship between the power of rubber-tired and other types of tractors would require special investigations. Since using the plow as the class interval in the grouping of tractors and of farms with tractors has considerable practical advantages, the plow may be retained in this capacity. Instead of the present indefinite plow, however, a plow expressed in definite numbers of adjusted drawbar horsepower

232 SUMMARY should be used as the class interval. In grouping tractors with steel wheels and crawlers by size, it is tentatively proposed to use 5.5 adjusted horsepower as the class interval and 4.12 horsepower as the low limit of the smallest size group. The development of the rubber-tired tractor is too recent to permit proposals with regard to the proper grouping of tractors of this type by size. It will usually be found rather disturbing to have farms with different numbers of tractors in the same type-of-power groups. The number of tractors per farm will then be used as a further criterion for grouping tractor farms by type of power. It can be shown that a certain tractor used as the main source of power may be profitable, while the same tractor would involve a loss if used as an auxiliary source of power, and vice versa. It may therefore frequently be necessary to use the proportion of the work performed by tractors to total power work as another attribute for grouping tractor farms by type of power. The proportion of tractor drawbar work to total drawbar work seems, in this case, to provide the best results. Grouping by the proportion of the work performed by tractors may be conveniently treated as subgrouping. The several classifying factors suggested for grouping farms by type of power indicate that the total number of type-ofpower groups of farms which may be needed for insuring adequate results is greatly in excess of the number distinguished by investigations to date. COMPUTING COST OF TRACTOR POWER. Another important task of a tractor study is a proper computation of the cost of operating tractors. It is usual in power studies to employ as the first cost of horses their price in the year of investigation, while for tractors the price in the year when the tractor had been bought is used for the first cost. Using this price causes considerable inaccuracies, when tractors bought at widely divergent levels are involved. When such divergence in prices occurs, the prices of the tractors studied should be adjusted for the changes in the price level of tractors between the time the tractors were bought and the year of investigation. Computing the rate of depreciation for tractors is the most complicated part of the problem of determining the cost of

SUMMARY 233 power. The rate at which the value of tractors declines as their age increases depends on several factors. The first important depreciation factor is the effect of humidity and of other external forces on the tractors, whether they are used or not used. The value of older tractors is affected by the fact that their work is less efficient than that of new up-to-date models. The depreciation in a certain year greatly depends, furthermore, on the amount of work done in that year by the tractor. T h e quality and the amount of care given to the tractor, the financial status of the farmer, and the prevailing rate of interest are other factors. Tractors of different type, to some extent also of different size, are affected to a different degree by the various depreciation factors. T h e baby-tractor is lighter in construction and therefore does not last so long. Crawlers are able to perform substantially more work during their life than wheel-tractors. Rubber-tired tractors probably also are more durable than tractors with steel wheels. The much-used straight-line method (the yearly charge to depreciation is determined by dividing the first cost by the estimated life) is inadequate in computing depreciation, for it disregards the reduced efficiency of older tractors. Moreover, the farmers' estimates of the life of tractors, upon which the computations of depreciation in the straight-line method are usually based, are seldom entirely reliable. A method for computing the rate of depreciation for tractors which attempts to take into consideration the declining value of the service of the tractor has therefore been devised by the present writer. As far as the life of the tractor is concerned, it is suggested that it should be estimated by the investigators, who have to use farmers' estimates of tractor life as well as other available material, as the basis for their judgment. The proposed rate of depreciation consists of two parts, a yearly one (fixed charge) and a per-hour-oj-work (variable) charge. Both charges are computed by applying constant percentages to the average between the first cost of the tractor and its remaining value (remaining value is the value of the tractor at the beginning of the year for which the depreciation charge is computed). It seems that all factors materially affecting wear and tear, both those independent of and those dependent

234 SUMMARY upon the amount of work done per year, are fairly taken care of by the proposed method. To utilize both the first cost and the remaining value in constructing the basis for the computations of the charge to depreciation results in a gradual decline of the yearly and hourly charges for tractors as their age increases, instead of an equal charge through all years of service, as provided by the straightline method. If the unweighted average between the first cost and the remaining value of the tractors be used as the basis for computing the charge to depreciation, the rate of depreciation in the last year of the life of the tractors is equivalent to somewhat more than half of the rate in the first year. By using a weighted average between the first cost and the remaining value, any other relation between the rates of depreciation in the last and the first years can be established. It is suggested to employ for all types and sizes of tractors, except perhaps the baby-tractors, a fixed charge that is equivalent to 7.5 percent per annum of the average between first cost and remaining value. The variable charge per hour of operation is equivalent to 5.34 percent of the same average, divided by the number of hours that the tractor can be used annually during a working life of ten years. Hence the variable charge is equivalent to 0.01 percent of the average between first cost and remaining value for a tractor which will have only scrap value, if used 534 hours annually during ten years. The variable rate would be only half as much for a tractor which is good for twice as much work. The stronger the tractor and the less the amount of annual work, the larger is the proportion of fixed charges to the total charge to depreciation, and vice versa. As to interest, the remaining value of tractors is recommended as the basis for computations, instead of half of the first cost, which is usually employed for this purpose. By this change the frequently occurring bias in favor of relatively new tractors is eliminated. As in the case of depreciation, the cost of tractor repairs depends on several factors. Some expense is involved independently of the work done. The amount of current work is the second factor. A very important factor is the age of the tractor, or, primarily, the total amount of previous work. The

SUMMARY 235 actual costs of repairs should not be used in power studies. They frequently show wide accidental variations. Moreover, variations in actual repair costs, caused by the age of tractors, create biases in favor of new and against older tractors. An equal charge per hour of operation, irrespective of the actual repair cost in the year of observation, seems to provide fairly good results. T h e total per-hour charge declines as the age of the tractor

increases, according to the proposed method. For the suggested reduction in the charges to depreciation and interest outweighs the inevitable increase in the cost of fuel, lubricant, and chore labor, while the cost of repairs, according to the proposal, and the cost of shelter remain unchanged. The reduction in the perhour cost of a wheel-tractor with about 10-11 adjusted horsepower is equivalent to about 24 percent, from the first to the last year of service. If the charge is computed per unit of power rather than per tractor, it is about IS percent less in the last year of service as compared with the charge in the first year, inasmuch as the power developed by tractors declines as their age increases. The decline in the per-hour charge for groups of tractors is still smaller, if it is considered that the annual use of older tractors, on an average, is less than that of newer ones. It is the task of each investigator to determine whether a reduction in the total charge, of the extent indicated, covers those direct (and indirect) losses and disadvantages of older tractors which it is desirable to offset by the reduction in the charge. If this is not the case, an adjustment of the total charge, by a change in the weights given to the first cost and to the remaining value for establishing the basis for computing the rate of depreciation, may easily provide a remedy. The costs of tractor power are easily distributed into fixed and variable charges, according to whether they are independent of or dependent on the amount of work performed. If the costs of horse power are distributed into fixed and variable charges according to the same principle, it will be found that the cost of horse power is almost fixed, while in the cost of tractor power the variable charges predominate. This result is quite different from that usually obtained in power studies (according to the latter, the cost of horse power is almost entirely

236 SUMMARY variable). The recognition of the diverging nature of the costs of tractor and horse power is the cornerstone of the theory of farm power. The value of a certain kind of tractor work to the farmer may vary, depending upon the cost of alternative power. Hence it may sometimes be advisable to charge the expenses of tractor power at different rates to different operations. This primarily pertains to belt work, for which the alternative power is different from the alternative power for drawbar field work. COMPARISON OF COST OF DIFFERENT TYPES OF POWER.

A

comparison of the cost of operating different sources of power, undertaken in order to ascertain the superiority of one of them, is usually made on the basis of crop acres. This basis, however, could provide reliable results only if the amount of power applied per crop acre were, on the average, equal on different typeo)-power farms. When only a few farms are included in the study, the results must evidently be accidental, because the amount of power spent per acre of various crops and the proportion of various crops on different farms vary greatly, even in the same type-of-farming area. Moreover, in many regions there is a tendency toward a divergence between the amount of power spent per crop acre on horse farms and that spent on farms with various kinds of tractors. In the Corn Belt, for example, tractor farms usually spend more power per crop acre than horse farms do, while in the Cotton Belt they use less than mule farms do. Hence reliability of conclusions cannot be ensured by increasing the number of farms in each type of power group. Data on the total cost of power on the investigated farms are always available. There are no insurmountable obstacles to computing also the amount of work done on those farms. By dividing the total cost by the total amount of power work, a comparison of the cost of power can be made on the basis of equal amounts of power work. A computation of the amount of power involves the use of some unit for measuring both mechanical and animal power. The horse-hour equivalent seems to be an adequate unit for this purpose. The power of a horse of certain weight and age, used as a unit, could be employed for reducing to a uniform basis even the power of horses (and mules)

SUMMARY 237 which are not of standard weight and age. Crop acres adjusted for variations in the amount of power, which are recommended as the basis for use in comparisons of the cost of power on farms with different types of power, are closely related to the horse hour equivalent. However, the crop acre is a thing entirely foreign to power. There is no reason to relate the cost of power to some base foreign to the latter, if a directly related basis is available, as in the form of horse-hour equivalents. ADJUSTMENTS OF COST OF POWER. Using tractors instead of horse power affects almost the whole farm organization. Labor mostly is the most strongly affected item. In the usual type of analysis based on comparison of the cost per crop acre, it is frequently attempted to consider the effect of the type of power on labor (and on machinery) by computing, instead of the cost of power per crop acre, the combined cost of power and labor (and/or machinery) per crop acre. Such broader comparisons are likely to be even less successful than similar comparisons of the cost of power alone. A considerable proportion of labor is commonly used in attending to productive livestock. The labor saved by the use of tractors instead of horses is usually small, as compared to that spent on livestock, and may easily be concealed by variations in the latter. To use the cost of power and labor (and/or machinery) per crop acre, therefore, would require the elimination of variations in the amount of labor used on productive livestock. Adjustments made for this purpose on the basis of animal units are inadequate, since animal units reflect the amount of feed and not the amount of labor used on livestock, and since the two do not run parallel. The total labor which is saved by operating tractors may be ascertained by subtracting the amount of man work done on tractor farms from the amount of man work which would be necessary if these farms were horse farms, and by increasing the residual figure in the proportion of labor available on horse farms to labor used on horse farms (labor used is labor available less the amount lost owing to weather conditions and seasonal variations in labor requirements). When the amount of labor available on tractor farms is subtracted from the amount of labor which would have to be available if these farms were horse

238 SUMMARY farms and if the ratio between labor available and labor used were the same on them as on horse farms, the amount of labor saved and gainfully employed is derived. The difference between the total labor saved and labor saved and gainfully employed is labor saved but not employed gainfully. Adjustments for machinery may be handled in a manner similar to the adjustments for labor. In some regions adjustments for yields may also be necessary. SIZE OF FARMS AS AFFECTING COST OF POWER. The amount of power (and/or labor and/or machinery) used per crop acre usually declines sensibly as the size of farms, as measured in crop acres, increases. The cost of power (and/or machinery) per unit of power, for example, per horse hour, likewise declines. There is, therefore, a cumulative decline in the cost of power per crop acre with the increase in the size of farms. This decline proceeds at different rates, and ends at different size levels, for farms with different types of power. Hence care must be exerted in order to prevent differences in the size of investigated farms from affecting the conclusions drawn from the data on the cost of power (and/or labor and/or machinery) per crop acre. Comparisons of data for groups of different type-of-power farms of unequal size must be definitely barred. Moreover, attention should be given to the fact that the results are likely to be the more favorable for tractors, the larger the average size of the farms compared. On the other hand, a considerable dispersion of individual farms about their average sizes may favor horses in the comparison. When, instead of the crop acre, the horse-hour equivalent is used as the basis for comparisons of the costs of power on different type-of-power groups, the effect of the size of farms on the cost of power is reduced, because the differences in the amount of power used per crop acre on small and on large farms are eliminated. But the cost of power per horse-hour equivalent also goes down as the size of farms increases, owing (1) to the greater number of hours that tractors and horses are used on large farms, (2) to the possibility of using larger tractors on larger farms, and (3) to the fact that the efficiency of tractors on larger farms shows proportionately greater increases

SUMMARY 239 than that shown by horses. Differences in the rate of the decline and in the level at which the decline ends also persist. Thus replacement of the crop acre by the horse-hour equivalent reduces, but does not eliminate, the chance that differences in the size of farms will affect comparisons of the cost of power on different type-of-power farms. So far as data on the amount of power used on farms are available, it seems logical to use in power studies the amount of power as the measure of farm size. Thus the general measure of the farm size, the crop acre, is stripped of still another function in power studies. The important effect of the size of farms, be it measured in crop acres or in amounts of power work, on the cost of power makes it desirable to use a small class interval in grouping farms by size. This would necessitate having many size groups. It happens but rarely, however, that power investigations do not reveal haphazard results, owing to insufficiency of the number of farms within the individual size groups. Moreover, a great extension of the number of farms included in studies is frequently impossible, not only on account of lack of means, but for other reasons (for example, limitations imposed by the requirement of a uniform area). The necessity both to eliminate the effect of the size of farms on the cost of power and to include a sufficiently large number of farms in each size group makes power studies considerably more difficult and the scope of the possible findings more limited than is frequently assumed. THE AREA. Replacement of the crop acre by the horse-hour equivalent as the basis for comparisons of the cost of power, proper grouping of the investigated farms by type of power, and utilization of adequate methods of computing the cost of power reduce the probability that improper selection of the area covered will greatly affect the findings. However, variations between different areas in the prices of feed, fuel, and other items of the cost of horse and tractor power, and in the length of annual use per horse or per tractor on similarly sized farms, makes strict adherence to the principle of selection of uniform areas indispensable.

APPENDICES

o re co li-) VD T-H

p* K

C i o w) N vO es — '

— f } >

O O ^ i O O C s O O s

—i O ©

• í « N «)

9

O

i'V ~ fMíNsrvjtvjfvjrvjfvcif^)

; +J >

>

' 9 ^ . "5 »

^ »

• £££ — »O O ^ O es es -h es es

ÍTt Oí

^

«O O O C- ro CO J

o H


M a a < < zn t o t

¡ ä s i
>x >» J2 -Û Í ß a -a -a 5» & _ . . . o u u

Bh E l çi « O V ^

Q w H

Q

S" S" S* o o o o o p¿ p£ pS & fc e á o S r t ^ S T í z i Z Z ;

Q

seto


o

t,"

* ^ tß ^ ' ^ fe =2 i IO ^ ' M K f :

PH

H en Pí O

?

fe; fe: fe: fe; Ö ß ß Ö C C R C

c a £ o

c a — >i C J5 fi a S -o & £ -Ö

c c s: -c

a a £ ¿s

_ „ o o o Z o f l z o i :

oo

a >> o H ,

S

g g g g g g g g

S

Pi

g rt Í5

S O >û es O to g fO —.->-« eN — W f W S ^ O o ^ ^ C í o o o >« VO CM ro ^ io o

o

o

e CS^ © © a

es

o l i W a ì d i i c I d r i '

^ ^ P H ^ ^ P H P m O H P K ^ Q H ^

g

j o S S S S o o o o o o á S

f S »

©

tf t

«í IO oo

M O O 8 1 g û ^ Zf? M- -o •o a w 5E Ïj :Ï ^ m

S£ s

| Ilj

i

o as

fia

g, O « 2 § E.

û M _ c a

-

"

i-2

s

l a_

III

11-

s «

o

»SI

v)wnMm0i«i«iaonvB)

M

m

8 '

2O c« oi Í < 2 M S E 2 j« M S

-

=• &-S •S ï 3 S O -

« c « — i> Q
v >» >> >> • . û. Û. cörtrtoj

ú E >• S > % g >> >. >. 3 3 9 3 3 ^ ü á s ^ i á i • » >-p >-p Hp t-p A M N. J. 1 J. 1 i i 1 - H N tó i ¿ I N N CS 2 ¿ « « « O IO

.

¿>
» —N »•>

¿mX

^

%6

May Nov. April Oct.

26-Aug. U-Oct. 1-M*y 1-Nov. J-April 23-Nov.

£

>

II

i

•a w> i< » s* K s S S s

S

l\j M N **•> «n *"» ¿N ¿N ¿N to —» Nô N¿ N¿ •a ^ C i l i

t;

- IS IK I h (Q £S.-s* *• i ' *i .9 .S .S .S .5 .9 * » «o * * * o o o o oje Ö u J3 I «• M n • J« fl XM ^n I I

Ü

S g

*C * «J 1 < £ •Í X —

5 dì
=(»

V X Ö

S ! S i

3

S s O 5 * BS

M M M M ,2 2

a 2

S ì Ì St Ü

ï S S S Ï ï S

•n r» N " 5 t 8 c a S

^^ O O fn O.Ï N "j5t « V) N . ' ' ' s ® M H " P M ") S .S .S 2 - 2 .2 i t i l l i g 9 3 8 S S c c q o o e a a S a a e g S s g s s

ï B

s= ag »

0

1

& Q. O O

S s si •«»^r • i i O o 00 rs 06 X t fc t o, o. o. a, 0o, °r Û. ¿ ¿ ¿ ¿ ¿ ririririri(4 «4 « S S Ä >V > > O O O 1

•s s

S

Is e No t>

É

C s H x

=3 M <


^ «e «e ¿J «M »M A •5 S S! 7 ^ ^

£

E 1)

=> »-i C)

o«M «Ni

« ft Oí » O, « »!

8m

S «

g H D 3S g a

5 S u -C W J3 Ü J3 u «c Ì3 ao oc4 © s s s

^ 3 fM «o ri -o ri

S - ä S o « S a Ss 2 S 5 g Ä £3 g2 ì £ S I * H O » ft, M On C O : fc

£

e 4;

z

ri

£

H

ï

e C ca

é

a

£

* „

2

»

£

OO

OO f >

rM

-o «

«o o

o

«n

Wisconsin Model E 16-30

k a

WISCONSIN FARM TRACTOR CO.

Wetmore 12-25

k m

H. A. WETMORE

21-Sept. 6-April 9-June

April June

On market Jan., 1937 Not shown in Neb. Tractor Tests, 1920-2»

9-Sept. Sept.

Sept.

7,1920

7.57

11.92

18,1920

12,1921

28,1920

28.86

24.62

29.39

17.39

12.6S

17.82

14.28

18.37

28.71

23, 1920 26.72

3-Sept. 29,1920

Disc., see Neb. Tractor Tests, 1920-23

k M

Uncle Sam 20-30

k «

Disc., see Neb. Tractor Tests, 1920-2»

Sept.

Not shown in Neb. Tractor Tests, 1920-30

M

U. S. TRACTOR AND MACHINE CO.

Sept.

! Rating changed to 18-30 (Not shown in Neb. Tractor Tests, 1920-2«

M

Townsend 15-30

k M

Toro 6-10

k

27-Oct.

19-June

June

Disc., see Neb. Tractor Tests, 1920-23

9.31

34.82 18.80 24.59

25, 1921 61.10 23,192] 30.46 25, 1923 38.56

16-June 16-May 16-May

June May May

Not shown in Neb. Tractor Tests, 1920-29 Not shown in Neb. Tractor Tests, 1920-29 Not shown in Neb. Tractor Tests, 1920-29

17.71

31.16

10, 1922 55.93

1-May

April

Not shown in Neb. Tractor Tests, 1920-21

M

30,1920

10.55 9.26 17.21 24.09 17.84 20.45

«ATEO

Drawbar H P

21.49 17.47 26.75 32.39 26.20 32.43

•

Rated Belt H.P.

8,1920 9, 1920 13, 1925 19, 1927 3,1929 8,1929

When Tested

May 28-June June 1-June May 7-May Oct. 12-Oct. April 24-May May 4-May

Not shown in Neb. Tractor Tests, 1920-29 [ Not shown in Neb. Tractor Tests, 1920-29 Not shown in Neb. Tractor Tests, 1920-29 Not shown in Neb. Tractor Tests, 1920-35 Not shown in Neb. Tractor Tests, t920-3f Not shown in Neb. Tractor Tests, 1920-35

Remarks

Já M Ji

TOWNSEND MANUFACTURING CO.

k

TORO TRACTOR CO.

k

Square Turn 18-35

k «

Samson Model M

k M

SQUARE TURN TRACTOR CO.

k

SAMSON TBACTOB CO.

Fuel Used

M

Russell 30-60 Russell Model C 15-30 Russell Model C 20-40

k

Rogers

k k tn

THE RUSSELL CO.

k «

ROCEBS TRACTOR AND TRAILER CO.

Heider Model C 12-20 Heider Model D 9-16 Heider Model 15-27 Rock Island 18-35 Rock Island G 2-15-25 Rock Island G 2-18-30

HOCK ISLAND PLOW CO.

Type of Tractor

13.91

10.12

14.26

11.42

6.06

14.70

7.45

27.86 15.04 19.67

24.93

8.44 7.41 13.77 19.27 14.27 16.36

1 R 9

M M

k « k n

— i 1 u

O t> O O*

31

5

-" S

11

— © © O* O« M H N t ^ ^

.9 •8

»

•Jt-v-vSS

Is

Number of Years

0.84 0.69

l o N f o N N Nf> i/> w> v> i*> v> min

IOV)W)MVI

11 Si

3 > 00*1N»
o Z

~ ^ ^

S

¿gl ill

M

-

IV

10.01 9.55 9.09 8.64 8.18

200 Hours Used per Year

|

• aa

* 00

I O N O S * N O M O I — 0> t»»

.2.2 Ills!

"i ^ »O

^O t- 80 ^ ©

IB

«tii!SE H6XB600

APPENDIX I I I SOME DETAILS OF T H E APPLICATION OF T H E RECOMMENDED METHOD OF COMPUTING T H E CHARGE TO DEPRECIATION* A. PROPORTION OP FIXED CHARGES TO TOTAL, IN PERCENT

Annual use, in hours

Tractor A

B

C

D

E

F

G

200 300 400 500

77.3 69.4 63.0 57.7

78.9 71.4 65.2 60.0

80.7 73.5 67.6 62.5

82.4 75.8 70.1 65.2

84.3 78.1 72.8 68.2

86.2 80.7 75.8 71.4

88.2 83.3 79.0 75.0

600 700 800 900 1,000

53.2 49.3 46.0 43.1 40.5

55.6 51.7 48.4 45.5 42.9

58.1 54.4 51.0 48.1 45.5

61.0 57.3 54.0 51.0 48.4

64.1 60.5 57.3 54.3 51.7

67.6 64.1 61.0 58.1 55.6

71.4 68.2 65.2 62.5 60.0

1,100 1,200 1,300 1,400 1,500

38.3 36.2 34.4 32.8 31.3

40.5 38.5 36.6 34.9 33.3

43.1 41.0 39.1 37.3 35.7

46.0 43.9 41.9 40.1 38.5

49.4 47.2 45.2 43.4 41.7

53.2 51.0 49.0 47.2 45.5

57.7 55.6 53.6 51.7 50.0

B . REMAINING VALUE IN PERCENT OP FIRST COST

Annual use, in hours

After five years for tractor A

B

C

D

E

F

G

200 300 400 500

56.0 51.5 47.2 42.9

56.8 52.7 48.7 44.8

57.6 53.9 50.3 46.8

58.5 55.2 51.9 48.7

59.3 56.5 53.5 50.7

60.1 57.6 55.2 52.7

61.0 58.9 56.8 54.8

600 700 800 900 1,000

38.8 34.7 30.7 26.9 23.1

41.0 37.3 33.6 30.0 26.5

43.3 39.9 36.5 33.3 30.0

45.6 42.5 39.5 36.5 33.6

48.0 45.2 42.5 40.0 37.3

50.3 48.0 45.6 43.3 41.0

52.7 50.7 48.8 46.8 44.8

1,100 1,200 1,300 1,400 1,500

19.4 15.8 12.3 8.9 5.5

23.1 19.7 16.5 13.3 10.1

26.9 23.8 20.7 17.8 14.9

30.7 27.9 25.1 22.4 19.9

34.7 32.2 29.6 27.2 24.8

38.8 36.5 34.3 32.2 30.1

42.9 41.0 39.1 37.3 35.4

• For hours averaged by the tractors studied, during a working life of ten years, see introductory remark to Appendix II. 256

B . R E M A I N I N G V A L U E I N P E R C E N T OF F I R S T C O S T ( C o n t i n u e d )

Annual use, in hours 200 300 400 500

After ten years for tractor A

B

C

D

E

F

G

21.7 14.8 8.3

22.9 16.6 10.5 4.9

24.2 18.5 13.0 7.7

25.5 20.4 15.4 10.6

26.9 22.3 17.9 13.6

28.2 24.2 20.4 16.7

29.5 26.2 23.0 19.7

6.0

9.5 5.4

13.0 9.5 6.0

16.6 13.6 10.6 7.7 4.9

600 700 800 900 1,000

...

C . T H E C H A R G E TO D E P R E C I A T I O N AND T H E R E M A I N I N G V A L U E OF TRACTOR U S E D 5 0 0 H O U R S P E R Y E A R , PER $ 1 0 0 OF F I R S T COST

Year [y charge, in dollars

Total charge per hour, in cents

Fixed

Variable

Total

Remaining value, in dollars

4 5

3

7.50 7.03 6.59 6.18 5.79

5.00 4.69 4.40 4.12 3.86

12.50 11.72 10.99 10.30 9.66

87.50 75.78 64.80 54.50 44.84

2.50 2.34 2.20 2.06 1.93

6 7 8 9 10

5.43 5.09 4.77 4.48 4.20

3.62 3.40 3.18 2.98 2.80

9.05 8.49 7.96 7.46 6.99

35.79 27.30 19.34 11.88 4.89

1.81 1.70 1.59 1.49 1.40

11

1.13«

0.76«

1.89«

3.00

1.35

Years of service

1 2

B,

• Scrap value is reached after the expiration of 28 percent of the eleventh year of service. The slight difference between the figures in part C of Appendix II and those of part C of Appendix III results from the use of one decimal in Appendix II and two decimils in Appendix III.

257

APPENDIX I V DERIVATION OF DEPRECIATION

FORMULAE

FORMULA WITH U N W E I G H T E D AVERAGE

Let Vo be the first cost, V, the value at the end of the rth year, V„ the scrap value at the end of the wth year (n years being the length of the life of the tractor), and x the required fraction (see p. 79). Then Fr_,-7r=y

"

-

0

(7o+Fr_0,

-

7

)

^

-

7

F

-

Adding Vo to both sides of the equation results in a geometric progression, as follows:

or, if h is any integer not greater than r, V9+ Vr = ( l

r r _ * + To),

-H)'2K" Hence,

,

*

n/V^+V,

258

FORMULA WITH W E I G H T E D AVERAGE

Let a be the weight given to the remaining value at the beginning of the year and (1 —a) the weight given to the first cost, each being expressed as a fraction of the sum of the two weights. Then V^-Vr-xiaVr-x+iX-aiV*] VT=Vr-x{\-ax)-V,{\-a)x I —a —

ri-a Vr=Vr-i(l-ax) + v A —

"I (l-a)xl

(1 — a) 7 o + a F r = a F r _ i ( l - a x ) + ( l - a ) K o ( l - a a : ) = [aF,_»+(l-a)Fo]

(I-ax)"

(l-o)V0+aVK=[aVo+(l-a)Vo](l-ax)» =

V0(l-ax)n (l-a)K0+aK„

ax--

'{l-a)Vo+aVn Vo

-TO-/'

250

(l-a)F0+aK„>

BIBLIOGRAPHY Allen, William, The Farm Business in Saskatchewan. Study No. 1: Survey of the Belbeck District. Regina, Saskatchewan, 1927. University College Agricultural Extension Bulletin 37. 100 pp. The Farm Business in Saskatchewan. Study No. 4 : Survey of the Swift Current—Gull Lake District. Regina, Saskatchewan, 1931. University College Agricultural Extension Bulletin 52. 134 pp. Annual Report of the Farm Management Service for Farmers in Southern Minnesota for the Year 1933. St. Paul, Minnesota. University of Minnesota Department of Agriculture, March, 1934. 31 pp. Barger, E. L., "A Survey of the Tractor Fuel Situation in Kansas." Agricultural Engineering, June, 1936, pp. 241-46. Bennett, M. K., Farm Cost Studies in the United States: Their Development, Applications, and Limitations. Palo Alto, California, 1928. Miscellaneous Publications of the Food Research Institute, California. 289 pp. Benton, A. H., R. H. Black, and Others, The Combined Harvester-Thresher in North Dakota. Fargo, North Dakota, 1929. North Dakota Agricultural Experiment Station Bulletin 225. 49 pp. Issued in cooperation with the United States Department of Agriculture. Black, J o h n D., "Agricultural Wage Relationships." The Review of Economic Statistics, 1936, No. 1 and 2, pp. 8-15 and 67-83. Blasingame, R. U., "Relation of Mechanical Progress in Agriculture to Land Utilization and Land Policy." General Conditions and Tendencies Influencing the Nation's Land Requirements. Part I of the Supplementary Report of the Land Planning Committee to the National Resources Board. Washington, 1936, pp. 39-47. Brody, Samuel, and Richard Cunningham, Growth and Development with Special Reference to Domestic Animals. XL Comparison between Efficiency of Horse, Man, and Motor, with Specific Reference to Size and Monetary Economy. Columbia, Missouri, 1936. Missouri Agricultural Experiment Station Research Bulletin 244. 56 pp. Case, H. C. M., R. H . Wilcox, and H. A. Berg, Organizing the Corn-Belt Farm for Profitable Production; Based on Studies of Farms in East-Central Illinois. Urbana, Illinois, 1929. Illinois Agricultural Experiment Station Bulletin 329, pp. 259-332. Cavert, W. L., Sources of Power on Minnesota Farms. St. Paul, Minnesota, 1930. Minnesota Agricultural Experiment Station Bulletin 262. 72 pp. 1935 Complete Costs and Farm Business Analysis on 39 Farms in Champaign and Piatt Counties, Illinois. Urbana, Illinois. College of Agriculture, University of Illinois. Mimeographed Publication. 66 pp. Cooperative Traitor Catalog. 22d annual ed. and previous editions. Implement and Tractor Trade Journal, Kansas City, Missouri, 1937. Cornell, F. D., Jr., Power on West Virginia Farms. Morgantown, West Virginia, 1935. West Virginia Agricultural Experiment Station Bulletin 267. 44 pp. Davidson, J . B., Life, Service and Cost of Service of Farm Machinery. Arnes, Iowa, 1929. Iowa Agricultural Experiment Station Research Bulletin 260, pp. 259-75. Agricultural Machinery, New York, 1931. Edgar V. Collins, and Eugene G. McKibben, Tractive Efficiency of the. 261

262

BIBLIOGRAPHY

Farm Tractor. Ames, Iowa, 1935. Iowa Agricultural Experiment Station Research Bulletin 189, pp. 257-333. Denker, C. H , and L. M. Ries, Bedeutung und Aussichten des Kleinschleppers in den Bäuerlichen Betrieben. Berlin, 1933. 41 pp. Diesel Power and Field Operating Costs. Bozeman, Montana, 1934. Montana Agricultural Experiment Station Bulletin 289. 16 pp. Ezekiel, Mordecai, Methods of Correlation Analysis. New York, 1930. 427 pp. Fain, John R., and W. A. Minor, Cost and Utilization of Farm Machinery. Athens, Georgia, 1931. Georgia University College of Agriculture Extension Division Bulletin 407. 32 pp. and Others, Utilization and Cost of Farm Power in Georgia. Athens, Georgia, 1933. Georgia University College of Agriculture, Extension Division Bulletin 434. 55 pp. Forty-Third Annual Report of the Purdue University Agricultural Experiment Station, Lafayette, Indiana, for the Year Ending June 30, 1930. Lafayette, Indiana, 1930. 116 pp. Gilbert, C. W., An Economic Study of Tractors on New York Farms. Ithaca, New York, 1930. New York (Cornell) Agricultural Experiment Station Bulletin 506. 80 pp. Also presented with Bulletin 507, Motor Trucks on New York Farms, as thesis (Ph.D., Cornell). Motor Trucks on New York Farms. Ithaca, New York, 1930. New York (Cornell) Agricultural Experiment Station Bulletin 507. 55 pp. Also presented with Bulletin 506, An Economic Study of Tractors on New York Farms, as thesis (Ph.D., Cornell). Grest, E. G., "Comments on Depreciation and Repairs of Combine Harvesters and Tractors on the Canadian Prairies." Scientific Agriculture, Vol. 13, No. 1., September, 1932. Ottawa, Canada, pp. 26-35. "Cost of Tractor Operation on Prairie Farms in Western Canada." Scientific Agriculture, Vol. 14, No. 2, 1933. Ottawa, Canada, pp. 83-5. Gross, Edward R., and Allen G. Waller, Tractor Farming in New Jersey: Selection and Care; Operating Costs and Place in the Farm Organization. New Brunswick, New Jersey, 1923. New Jersey Agricultural Experiment Station Bulletin 386. 24 pp. Hall, Orville J., Cost of Producing Rice in Arkansas in 1927. Fayetteville, Arkansas, 1931. Arkansas Agricultural Experiment Station Bulletin 266. 47 pp. Hampson, C. M., and Paul Christophersen, Tractor and Horse Power in the Wheat Area of South Dakota. Brookings, South Dakota, 1932. South Dakota Agricultural Experiment Station Circular 6. 39 pp. Handschin, W. F., J. B. Andrews, and E. Rauchenstein, The Horse and the Tractor. An Economic Study of Their Use on Farms in Central Illinois. Urbana, Illinois, 1921. Illinois Agricultural Experiment Station Bulletin 231, pp. 171-223. Hauser, W., Die Kosten der Traktorhaltung in schweizerischen Gutsbetrieben. Bericht 10 der schweizerischen Stiftung "Trieur." Brugg, Aargau, 1933. 75 pp. Hauter, L. H., A. L. Walker, and O. V. Wells, Production Requirements, Costs, and Returns from Dry-Land Farming in Eastern New Mexico. Part II of Economics of Agriculture on Dry-Land Farms in Eastern New Mexico. State College, New Mexico, 1930. New Mexico Agricultural Experiment Station Bulletin 187. 59 pp. Hopkins, E. S., J. M. Armstrong, and H. D. Mitchell, Cost of Producing Farm Crops in the Prairie Provinces. Ottawa, Canada, 1932. Dominion of Canada Department of Agriculture Bulletin 159. New Series. 78 pp.

BIBLIOGRAPHY

263

Hurst, W. M., and L. M . Church, Power and Machinery in Agriculture. Washington, D.C., 1933. United States Department of Agriculture Miscellaneous Publication 157. 39 pp. Hutson, J. B., W . G. Finn, a n d Z. L. Galloway, An Economic Study of Crops and Livestock in the Purchase Region of Kentucky. Lexington, Kentucky, 1928. Kentucky Agricultural Experiment Station Bulletin 289, pp. 307-433. Issued in cooperation with the Division of Farm Management and Costs, Bureau of Agricultural Economics, U. S. Department of Agriculture. Jasny, N., Der Schlepper in der Landwirtschaft, seine Wirtschaftlichkeit und weltwirtschaftliche Bedeutung. P. Parey, Berlin, 1932. 1SS pp. (Reichsministerium f ü r Ernährung und Landwirtschaft. Berichte über Landwirtschaft, N.F., 62. Sonderheft.) "Tractor versus Horse for Farm Power." American Economic Review, December, 193S, pp. 708-23. Johnston, P. E., and K. H . Myers, Harvesting the Corn Crop in Illinois: An Economic Study of Methods and Relative Costs. Urbana, Illinois, 1931. Illinois Agricultural Experiment Bulletin 373, pp. 355-405. Issued in cooperation with Division of Farm Management and Costs, Bureau of Agricultural Economics, U. S. Department of Agriculture. and J. E. Wills, A Study of the Cost of Horse and Tractor Power on Illinois Farms. Urbana, Illinois, 1933. Illinois University Agricultural Experiment Station Bulletin 395, pp. 269-332. Kifer, R. S., " T o Determine the Relative Economy of Harvesting Small Grain with a Combined Harvester-Thresher and a Binder, or Header and Stationary Thresher." Research in Farm Management—Scope and Method. Edited by J. D. Black. New York, 1932. Social Science Research Council Bulletin 13, pp. 211-16. Kisourin, I. J., and G. M. Losa, Planning the Organization of a Section on State Farms. Moscow, 1934. Lamont, T . E., "Ways of Reducing the Cost of Producing Apples." Farm Economics, Vol. 69, February, 1931. Ithaca, New York. Cornell University College of Agriculture, pp. 1481-84. Landerholm, E. F., The Economic Relation of Tractors to Farm Organization in the Grain Farming Areas of Eastern Washington. Pullman, Washington, 1935. Washington Agricultural Experiment Station Bulletin 310. 51 pp. Lloyd, O. G., and L. G. Hobson, Relation of Farm Power and Farm Organization in Central Indiana. Lafayette, Indiana, 1929. Indiana Agricultural Experiment Station Bulletin 332. 37 pp. Long, Lewis E., Farm Power in the Yazoo-Mississippi Delta. A. & M. College, Mississippi, 1931. Mississippi Agricultural Experiment Station Bulletin 295. 30 pp. Issued in cooperation with the United States Department of Agriculture. McCuen, G. W., and E. A. Silver, Rubber-Tired Equipment for Farm Machinery. Wooster, Ohio, 1935. Ohio Agricultural Experiment Station Bulletin 556. 37 pp. Mills, Frederick C\, Statistical Methods. London, Pitman, 1930. 604 pp. Murdock, H. E., Mechanical Tests on Tractor Farming Equipment. A Progress Report. Bozeman, Montana, 1931. Montana Agricultural Experiment Station Bulletin 243. 52 pp. Myers, W. I., An Economic Study of Farm Tractors in New York. Ithaca, New York, 1921. New York (Cornell) Agricultural Experiment Station Bulletin 405, pp. 53-134. Nebraska Agricultural Experiment Station, Nebraska Tractor Tests, 1920— 1936. Lincoln, Nebraska, 1937. Nebraska Agricultural Experiment Station Bulletin 304, and earlier editions. 38 pp.

264

BIBLIOGRAPHY

Peters, A., and R. Tismer, Arbeitsverfohren und Arbeitsleistungen m der Landwirtschaft. Ergebnisse aus der Arbeit der Betriebs-Abteilung der Deutschen Landwirtschaftgesellschaft auf dem Gebiete der Landarbeit. Zweite Auflage. Deutsche Landwirtschaftsgesellschaft. Berlin, 1930. 328 pp. Operations and performances in agriculture. Works of the German Society for Agriculture. Fond, George A., G. A. Sallee, and C. W. Crickman, An Economic Study of Crop Production in the Red River Valley of Minnesota. St. Paul, Minnesota, 1931. Minnesota Agricultural Experiment Station Bulletin 282. 110 pp. Procter, Robert C., Samuel Brody, and Others, Growth and Development with Speäal Reference to Domestic Animals. XXXIII. Efficiency of Work Horses of Different Ages and Body Weights. Columbia, Missouri, 1934. Missouri Agricultural Experiment Station Research Bulletin 209. 32 pp. Research Method and Procedure in Agricultural Economics. 2 vols. New York, 1928. Social Science Research Council. Advisory Committee on Social and Economic Research in Agriculture. Reynoldson, L. A., W. R. Humphries, and Others, Utilization and Cost of Power on Corn Belt Farms. Washington, D C., 1933. United States Department of Agriculture Technical Bulletin 384. 60 pp. Utilization and Cost of Power on Mississippi and Arkansas Delta Plantations. Washington, D.C., 1933. United States Department of Agriculture Technical Bulletin 497. 47 pp. Robson, H. R., and G. L. Shanks, "The Efficiency of Use of Farm Power." Scientific Agriculture, Vol. 14, No. 10, 1934. Ottawa, Canada, pp. S6S-68. Saliers, E. A., Depreciation, Printifiles and Applications. New York, 1923. Ronald Press Co. S90 pp. Saville, R. J., and G. H. Reuss, Tractors and Trucks on Louisiana Rice Farms, 1929 (With Supplementary Data on Labor Requirements). Baton Rouge, Louisiana, 1930. Louisiana Agricultural Experiment Station Bulletin 218. 39 pp. Schwantes, A. J., and G. A. Pond, The Farm Tractor in Minnesota. St. Paul, Minnesota, 1931. Minnesota Agricultural Experiment Station Bulletin 280. 82 pp. Sjogren, O. W. "Why Standardize Tractor Ratings?" Agricultural Engineering, Vol. 1, No. 4,1920. St. Joseph, Michigan, pp. 6-68. "Tractor Testing in Nebraska." Agricultural Engineering, Vol. 2, 1921, pp. 34-36. Smith, C. W., and Lloyd W. Hurlbut, A Comparative Study of Pneumatic Tires and Steel Wheels on Farm Tractors. Lincoln, Nebraska, 1934. Nebraska Agricultural Experiment Station Bulletin 291. 40 pp. Smith, Dwight D., and Mack M. Jones, Power, Labor and Machine Costs in Crop Production, Linn County, Missouri, 1930. Columbia, Missouri, 1933. Missouri Agricultural Experiment Station Research Bulletin 197. 48 pp. Sommerfeld, H. B., "Economic Aspects of the Horse Industry in Western Canada." Proceedings of the Fifth Annual Meeting of the Canadian Society of Agricultural Economics. Regina, Saskatchewan, 1933, pp. 82-95. Starch, E. A., Farm Organization as Affected by Mechanization. Bozeman, Montana, 1933. Montana Agricultural Experiment Station Bulletin 278. 102 pp. Issued in cooperation with the Division of Farm Management and Costs, Bureau of Agricultural Economics, United States Department of Agriculture. Statistical Abstract of the United States. Washington, D.C. United States Department of Commerce, Bureau of Foreign and Domestic Commerce. Stephens, P. H., Farm Production Costs in Oklahoma, 1931. Stillwater, Oklahoma, 1933. Oklahoma Agricultural Experiment Station Bulletin 208. 56 pp.

BIBLIOGRAPHY

265

Issued in cooperation with the Division of Farm Management and Costs, Bureau of Agricultural Economics, United States Department of Agriculture. Tolley, H. R., "To Determine the Economy of Using Tractors in a Specified Type-of-Farming Area." Research in Farm Management—Scope and Method. Edited by J. D. Black. New York, 1932. Social Science Research Council Bulletin 13, pp. 204-10. and L. M. Church, Tractors on Southern Farms. Washington, D.C., 1922. United States Department of Agriculture Farmers' Bulletin 1278. 26 pp. Motor Trucks on Corn-Belt Farms. Washington, D.C., 1923. United States Department of Agriculture Farmers' Bulletin 1314. 18 pp. and L. A. Reynoldson, The Cost and Utilization of Power on Farms Where Tractors Are Owned, 286 Farms—Ohio, Indiana, Illinois—1920. Washington, D.C., 1921. United States Department of Agriculture Bulletin 997. 61 pp. Washburn R. S., and R. S. Kifer, Utilization of Tractors and Cost of Tractor Power on Grain Farms (Northern Great Plains and Pacific Northwest, 1933). Washington, D.C., 1936. United States Department of Agriculture, Bureau of Agricultural Economics. Mimeographed. 32 pp. and H. D. Scudder, Cost of Producing Winter Wheat and Incomes from Wheat Farming in Sherman County, Oregon. Washington, D.C., 1927. United States Department of Agriculture Bulletin 1446. 40 pp. Cost of Using Horses, Tractors and Combines on Wheat Farms in Sherman County, Oregon. Washington, D.C., 1926. United States Department of Agriculture Bulletin 1447. 44 pp. Wright, K. T., and P. E. Aylesworth, 1934 Tractor Costs on 66 Michigan Farms. East Lansing, Michigan, 193S. Mimeographed Report of the Michigan Agricultural Experiment Station. 9 pp. Young, E. C., and G. W. Collier, Labor and Power Used in Crop Production in Central Indiana. Lafayette, Indiana, 1933. Indiana Agricultural Experiment Station Bulletin 378. 28 pp. Issued in cooperation with the Bureau of Agricultural Economics, United States Department of Agriculture. Zink, Frank J., E. L. Barger, June Roberts, and T. E. Martin, Comparative Field Tests of Rubber Tractor Tires and Steel Wheels. Manhattan, Kansas, 1933. Mimeographed Contribution 67 of the Department of Engineering, Kansas State College. 12 pp.

INDEX Acre, as unit of measurement of tractor power, 16 Advance-Rumeley Thresher Company, 242 Agriculture, intensive, 20 Alfalfa: and machinery, 193; power requirements, 151, 1S3 Allis-Chalmers Manufacturing Company, 242 American Society of Agricultural Engineering, 32-36, 231, 242 Appendices, 241-S9 Area, 239; selecting the, 224-28, 239 Aultman-Taylor Machinery Company, 243 Avery Company, 243 Baker (A. D.) Company, 244 Barger, E. L., cited, 92 Barley, power requirements for, 1S1 Bates Machine and Tractor Company, 244 Bear Tractors Company, 244 Belt power, 215 Belt work, 161-62, 200 Bennett, M. K., cited, 56 Benton, A. H., et al., cited, 65 Best (C. L.) Tractor Company, 244 Bibliography, 261-65 Black, J. D., cited, 180 Blasingame, R. W., 40 Bradley Tractor Company, 244 Brody, Samuel, and Richard Cunningham, cited, 173 Bureau of Labor Statistics, farm machinery data published by, 59-61

Class interval, 41-45 Cleveland Tractor Company, 246 Clover seed, power requirements of, 153 Coleman Tractor Company, 247 Combines, 191, 194 Co-operative Tractor Catalogue, 33, 60-61

Corn, 227; acre equivalent, 153, 169, 185; labor required for raising, 183; machinery and, 192; power requirements of, 150, 151, 169; tractor cultivation of, 8 Corn Belt, xii, 6, 26, 31, 40, 85, 92, 93, 105, 108, 138, 150, 155, 163, 165, 182, 184, 185, 216, 202, 227, 236 Cornell, F. D., Jr., cited, 14 Com pickers, 191 Costs adjustments for machinery, 190-95 biases in comparisons of, 152-58 differences in, 141 different tractor operations, 236 drawbar work, 162-67 farm size and, 178-79, 199-223; effect on operating, 222-23; effect on power, 199-223 fuel, 235 horse and tractor, compared, 132 horse and tractor power, 201 labor, 180-90, 223; compared, 142; per crop acre, 135 ff; proposed method of adjusting, 186-90 machinery: as compared with labor, 191; for different crops, compared, 142; per crop acre, 135 ff measurement of, 218; precautions in, 218; productive mean units as measure, 208 operating; machinery, 223; tractor

Canada, Department of Agriculture of, 22, 90 Case (J. I.) Company, 244 Case (J. I.) Plow Works Company, 244 Case (J. I.) Threshing Machine Company, 245 Caterpillar Tractor Company, 245-46 Cavert, W. L., cited, 114 Charts, 32, 59, 69, 76, 109, 119, 120, 136, 140, 154, 160, 161, 201, 204, 210

and horse, 134 power: adjustment for labor, 18090; compared, 142; in horse-hour equivalents, 208; on tractor and horse farms, 211-12; per crop acre, 135 ff; variations, 144; variations per crop acre, 205 267

INDEX

268

Costs (Continued) tractor fuel, 235 tractor power, 235 unit size of farms and, 178-79 variants, 125-33 C o t t o n : acreage in Georgia, 157; power requirements, 150, 151, 156 Cotton Belt, 150, 236 Cover crops, power requirements of, 150 Crawlers: predominate in Pacific States, 12; prices of, 60 Crop acre, 237 ; as unit of measurement, 208; shortcomings as basis for measurement of cost oi |xjwer, 122-61; variations in amount of power per, 149-52 Crops: intertilled, 5; row, 4, 5, 55; variations in labor required to cultivate, 182; yields, 197-98, 238 Dairy farmers, 158 Davidson, J. B., 19, 64-65 Davidson, J. B., et at., cited, 9, 10, 12, 64 Deere (John) Tractor Company, 247 Denker, C. H., and L. M . Ries, cited, 92, 94 Depreciation, 58, 62-94, 115, 232-34 computation of, 73-74; correct method, 63-64, 256-57 factors in, 63-71 formulae, 258-59 measurement of, 234; inventory method, 62; straight-line method, 62

rates of, 72, 77 ; total annual, 79-84 Diesel engines, 12 Duplex Machinery Company, 247 Eagle Manufacturing Company, 247 Efficiency, tractive, defined, 9 Electric Wheel Company, 247 Emerson-Brantingham Company, 248 Ezekiel, M., 144 Fain, J . R., and W. A. Minor, cited, 92 Fain, J . R., et at., cited, 3, 8, 15, 124, 132, 150, 156, 157, 220 Farmers: tractor, 194 Farm power, costs, 6 Farms big team-hitch, 160, 227

Farms (Continued) corn belt, 143, 158-67, 169, 209, 219, 220, 221

four-plow tractor, 207 general-purpose tractor, 139, 164, 182, 196, 202, 204, 209, 210, 221 grouping, 131, 225-26; by size, 220, 222; by types of power, 48-56, 122

horse, 126, 139, 142, 160-62, 169, 182, 186, 192, 194, 202, 204, 209, 210-12 horse and tractor, compared, 8, 154 horse-and-tractor, xx horse-and-tractor and horse, compared, 153 horse-operated, 197 Illinois, 184, 196, 214, 226 labor on, xiv, 180-90 mechanized, xix, 52-53, 198 minimum sizes in power cost measurement, 218-20 mule, 157, 236 mule-and-tractor, 157 Northwestern, 227-28 Oklahoma, 197 power, xix, 172; cost and amount, 158-67; differences in cost of, 210; distribution as to, 52; size as affecting cost of, 238-39; variation in amount used, 128 row crops, xvii size, 164 size groups, 136, 140, 204 small, 215 tractor, 141, 160-62, 164-65, 169, 182, 186, 189, 191, 194, 197-200, 202, 204, 211-12; small, 200; three-plow, 164, 165, 202, 204; two-plow, 164-65, 199-200, 202, 204 tractor-and-horse, xx, 53-54, 126-27, 142, 160-61, 169, 192-94, 198 trucks on, 127, 158 yields (tractor), 197-98 Farm Tractor Rating Code, 32-36 Farm with tractors, defined, xx Fate-Root-Heath Company, 248 Fixed charge, defined, 75 Foote Bros. Gear and Machinery Company, 248 Ford Motor Company, 248

269

INDEX Four Drive Tractor Company, 248 Frick Company, Inc., 248 Fuel, IS, 21, 106-07 Gilbert, C. W., cited, 15, 62-63, 69-71, 73, 85, 86, 88, 97, 117, 168, 236 Grains, 55-56 Gray Tractor Company, 248 Great Plains, 9, 101 Grest, E. G., cited, 22, 63, 73-75, 77, 80, 81, 82-83, 90, 102, 105, 254, 255 Gross and Waller, cited, 85 Hall, O. J., cited, 168 Hampson, C. M., and Paul Christophersen, cited, 53, 96, 101, 124, 175 Haulage, 159-61; tractor, 132, 158 Hauser, W., cited, 86, 92, 98 Hay, 169; labor required for raising, 182; machinery and, 193; power requirements, 150, 151, 153 Holt Manufacturing Company, 248 Hopkins, E. S., et al., cited, 22, 90, 97, 102, 104, 206 Horse farms, xii, xv, xvi, xvii, xviii; defined, rix Horse power: as measure of tractor power, 29-30; as unit of tractor movement, 42 ; in power studies, 36-38 Horses age, in relation to power, 173 cost of: keeping, 124; operating, in Corn Belt, 118 haulage, 159-61 on small farms, 213-14 power, 236; variations in, 15 ; weight as indicator of, 173 price, 232 tractors: compared with, 129-33, 135 ff, 148; displaced by, 125-26 Huber Manufacturing Company, 249 Hutson, J. B., et al., cited, 151 Indiana Silo and Tractor Company, 249 Interest, 94-96, 115; basis for computation of, 234 International Harvester Company, 24950 Inventory method, 69-70

Jasny, N., cited, 50, 63, 83, 124, 139, 158; method recommended for computing costs, 74-79 Johnston, P. E., and K. H. Myers, cited, 65 Johnston, P. E., and J. E. Wills, cited, xv-xvi, 3, 9, 14, 49, 69, 92, 100, 126, 137-39, 141, 182, 197, 207, 211, 220, 222,

226

Kafer, power requirements for raising, 151 Kansas State College, 91 Kentucky, power requirements for various crops in, 150-51 Kinnard and Sons Manufacturing Company, 250 Kisourin, I. J., and G. M. Losa, cited, 14 Labor, xvi, 142, 180-90 Agricultural Adjustment Act and, 180 costs of, 223; per crop acre in Com Belt, 182-83 depression and, 180 livestock and, 182 saved: and gainfully employed, 187; by tractors, 185 La Crosse Tractor Company, 250 Landerholm, E. F., cited, 7, 35, 88, 98, 152 Laslie, Anne, 243 Lauson (John) Manufacturing Company, 251 Livestock: feed required, as basis of cost of labor, 195-96; necessity for, in tractor studies, 196; variation in labor used on, 195-99 Lloyd, O. G., and L. G. Hobson, cited, 14, 114, 153, 154 Long, L. E., cited, 15, 88, 99, 125, 176, 197 McCuen, G. W., and E. A. Silver, cited, 12 Machinery, xvi, xvii, 142; adjustments for, 238; average costs and, 194; change in prices of, 62; cost basis vs. amount basis in tractor studies, 194; costs of operating, 191-95, 223 Massey Harris Company, 251

270

INDEX

Methodology, xi, xix, xx, 6, 68, 96, 122-23, 178-79, 230-39; "approach from the simple" procedure, 122, 125-33; "approach from the whole" procedure, 123, 133-48; labor costs, formulae for ascertaining, 187-90; machinery costs and, 194; size of farm averages, 211; terminology, xix Methods: formulae, 79-80; determining the life of a tractor, 89; measuring costs, 77-81; straight-line, 71 Minneapolis-Moline Power Implement Company, 151 Minneapolis Steel and Machinery Company, 252 Minneapolis Threshing Machine Company, 252 Moline Plow Company, 252 Monarch Tractor Company, 252 Montana Agricultural Experiment Station, 10 Mules, 15 Murdock, H. E., cited, 20, 37 National Resources Board, xiii Nebraska, 11; tractor law, 31; tractor tests, 32, 39, 242 Northwest, 227 Oats: labor required to raise, 183; machinery and, 192; power requirements, 150, 151, 153 Oklahoma, power requirements for various crops in, 150-51 Oliver Farm Equipment Company, 252 Pacific Northwest, 89, 91, 101 Pacific States, 12 Parrett Tractor Company, 252 Peak-breaking, 50 Peanuts, power requirements for raising, 150 Plantations: cotton, 105-6; delta, 147, 168 "Plow," abstract, as measure of tractor power, 16-29, 38; advantages, 18; defects, 18, 22, 42, 230 Plowing: depth of, 20, 26; tractor performances in, 23 Plows, 230; actual number as measure of tractor power, 20-24; factors affecting number a tractor can pull,

Plows (Continued) 19; size of, 19; tractor speed and, 20; tractor manufacturers' recommendations of number to be used, 25 Port Huron Thresher Company, 252 Potatoes, 227 Power affected by other factors of agricultural production, 180 amount: effect of farm size on, 199-208; in relation to crop yields, 197-98 causes of inefficient utilization, 199 costs, xvii, xviii, xix, 50-52, 58, 14647, 178, 179, 229, 232-37; adjustments in, 237; averages of, 20918; biases in comparisons, 152-56; curves, 212-13, 217; equal, may have divergent meanings, 57-121, 224; farm groups and, 200; farm size and, 199-223; general-purpose tractor farms, 209; horse and tractor, 201; large farms, 200; measurement of, 122-23, 211-12, precautions in, 218; operating, 123-45; per crop-acre, 144-45; per crop-acre in com belt, 160; relative, xvi; variations, 205 curves of, 201 defined, 18 determination of, difficult, 229 drawbar, 162-67 horse and tractor: compared, 16970; costs compared, 155-58 horse-hour equivalent as unit of measurement, 170-79 mule, 150 seasonal distribution of, 155-56 tractor, xvi, xviii, 150 types of, 161-62 type-of-power groups, 202 type-of-power work, 199 variations in amount, 144, 169; in amount per crop-acre, 158; in requirements, 15, 203-4 Procter, R. C., et al., cited, 173 Repairs, cost of, 234-35; age, effect of, 104; computation of, 100-104; data on, 104-6; factors affecting, 96 ff; per tractor type, 106 Research, prerequisites for, xvii

INDEX Reynoldson, L. A., et al., cited, 3, 5, 6, 16, 26, S3-S4, 62, 63, 71, 75, 82-83, 85, 88, 92, 93, 97, 100, 105, 106, 115, 119, 125, 130, 134, 142, 147, 149, 157, 159-60, 165, 167, 168, 182, 183, 199, 202, 205, 209, 210, 213, 216, 220, 221, 226, 254 Rice, power requirements of, 55-56 Rice farming, 168 Robson, H. R., and G. L. Shanks, cited, 31 Rock Island Plow Company, 253 Rogers Tractor and Trailer Company, 253 Rubber tires, duration of, 13 Russell Company, The, 253 Rye, power requirements of, 153 Saliere, E. A., cited, 67, 71, 79 Samson Tractor Company, 253 Sa ville, R. J., and G. H. Reuser, cited, 3, 86, 168 Schwantes, A. J., and G. A. Pond, cited, 49, 61, 66, 68-69, 92, 97, 106, 110, 167, 220 Shippler, M. M., 91 Silage, power requirements of, 150 Sjongren, O. W., 33 Smith, C. W., and L. W. Hurlbut, cited, 12 Smith, D. D., and M. M. Jones, cited, xx, 8, 53, 62, 65, 66, 75, 83, 88, 92, 96, 101, 130, 143, 168, 170, 185, 187, 192, 194, 207, 219 Society of Automotive Engineers, 32, 231, 242 Soil cohesion, 19-20, 24, 26, 230; in different types of soil, 19 ; in relation to measurement of power, 17 Sommerfeld, H. B., 54 Sorghum, power requirements of, 150, 151 Southeast, 227 Southwest, 227 Soviet Russia, 14 Soy beans, machinery and, 193 ; power requirements, 151 Scuare Turn Tractor Company, 253 Starch, E. A., cited, 10, 26, 66, 90-91, 96, 152 Stephens, P. H., cited, 87, 151, 197 Sveet potatoes, power requirements of, 150

271

Threshers, 185 Timothy seed, and machinery, 193 Tobacco, power requirements of, 150, 151 Tolley, H. R., xi, 89, 185 Tolley, H. R., and L. M. Church, cited, 158 Tolley, H. R., and L. A. Reynoldson, cited, 85, 158 Tomatoes, power requirements of, 15051 Topography, and tractors, 230 Toro Tractor Company, 253 Townsend Manufacturing Company, 253 Tractor-combine, 184-85 Tractor Rating Code, 40, 231 Tractor advantages, xvi; of crawler, 11-12; of general-purpose, 4-6, 7; of ordinary, 4-6; of rubber-tired, 1213; of steel-wheel and crawler compared, 11 appreciation, 73 "baby," 43, 45, 89, 233 belt work, xiv, 114-1S, 156, 159, 161-62, 200

breakdowns, 67 business recession, 8 capacity of, 20 changes in value of service, 67-70 classification of, 3, 16, 26 costs: biases in comparisons of, 15258; drawbar work, 162-67; farm size and, 178-79, 199-223; fuel, 235 ; labor, 180-90, 185, 223, for different crops, 142, per crop acre, 135 ff; machinery: adjustments for, 190-95, compared with labor, 191, for different crops, 142, per crop acre, 135 ff; measurement of: precautions, 218, productive man units in, 208; power, 178, adjustment for labor, 180-90, for different crops, 142, horse and tractor compared, 132, 154, 201, 211-12, horse-hour equivalents, 208, per crop acre, 135 ff, variations, 144, variations per crop acre, 205; repairs, 11, 15, 97; variants, 125-33 crop specialization, 225 depreciation, 62-83, 232-34; age as affecting, 64-71; formulae for

272

INDEX

Tractor (Continued) method recommended, 2S8-S9; Grest's method, 73-74, 76; inventory method, 62, 69-73; main factors affecting, 63-64; method of computing, 256-57; obsolescence, 58, 62-94; rates of, 74-84; recommended method, 74-84; reducing balance method, 71-72; straight-line method, 62; "sum-ofyear-digits method," 72; total annual rate of, 79-81; use, independent of, 63 discontinued models, 8 durability, 64-67, 88 efficiency, 13, 78-79 farms, xvii, xviii, 3; and farm distribution, 4 Fordsons, 28 four-wheel, 9 fuel, 15, 21, 106-7 general-purpose, xviii, 3, 4, 12, 46, 91, 106, 135, 139, 158, 216, 229 grouping of, 37, 45-47; by horsepower, 44; by items of cost, 11521; by size, 16; by type of power, 229; on plow basis, 28 haulage, 158, 159-61 horse equivalents of, xiv, 148, 173 ff, 206 horsepower of, 10-11; as measure of tractor power, 36-38; manufacturers' rating, 32-36; rated and adjusted, 241-53 horses, compared with, 129-33 investigations, 122 length of life, 63-71; farmers' estimates, 84-94 lubrication, 15 models not changed every year, 26 mules compared with, 147 number on one farm, 48-49 obsolescence, 8, 63-64, 66-68, 74, 81 old, 112-13, 139-40 performance, 14; compared with horses, 175, 177 ; of rubber-tired and others compared, 21-22; of three-plow and four-plow, 23; of wheel tractor and crawler compared, 10 power, xiv, 9, 150, 214; auxiliary source of, 174; average, 27; in

Tractor (Continued) relation to speed, 25; measurements, 122; types of, 127-28; variations in, 24 prices, 59 rating, 29, 40 recommendations for proper procedures in investigations of, 145-48 repairs, 96-106; rolling country, 157 row crops, 4, 5 size, xviii, 7, 14-47, 81, 229-230 speeds, 12, 18-19; differences in, 21 studies: Barger, 92; Bennett, 56; Benton et al., 65 ; Brody and Cunningham, 173; Canadian, 23; Cavert, 114; Com Belt, 5, 16, 19, 50, 97, 115, 116, 125, 127, 130-32, 143, 149, 159, 161-62, 163, 173, 182, 199, 203, 205, 209, 211, 213, 215-16, 226; Cornell, 14; Davidson, 19, 64-65; Davidson et al., 9, 10, 12, 64; Denker and Ries, 92, 94; Fain and Minor, 92; Fain et al., 3, 8, 15, 124, 132, 150, 156, 157, 220; Georgia, 3, 15, 92, 124, 132, 1S6, 220; Gilbert, 15, 62-63, 69-71, 73, 85-86, 88, 97, 117, 168, 226; Grest, 22, 63, 73-75, 77, 80, 82-83, 90, 102, 105, 254, 255; Gross and Waller, 85; Hall, 168; Hampson and Christophersen, 53, 96, 101, 124, 175; Handschin et al., 19; Hauser, 86, 92, 98; Hopkins, 97, 206; Hopkins et al., 22, 90, 97, 102, 104, 206; Huret and Church, 40; Hutson, 151; Illinois, xv, xvi, 3, 6, 9, 14, 49, 73, 92, 115, 116, 138, 139, 143, 159, 172, 19596, 207, 211, 213-14, 220, 221, 222-23; Illinois Agricultural Experiment Station, 19; importance of selecting area, 224-28; Indiana, 28, 54, 131-32, 153, 167; Jasny, 50, 63, 83, 124, 139, 158; Johnston and Myers, 65-66; Johnston and Wills, xv-xvi, 3, 6, 9, 14, 49, 92, 100, 126, 137, 138. 141, 182, 196, 207, 211, 220, 222, 226; Kisourin and Losa, 14; Landerholm, 7, 35, 88, 98, 152; Lloyd and Hobson, 14, 114, 153, 154; Long, 15, 88, 99, 125, 176, 197; Louisiana, 85;

INDEX Tractor (Continued) McCuen and Silver, 12; Minnesota, 66, 110, 114, 167-68, 220, 227 ; Mississippi, 88, 92, 99; Missouri, 8, S3-S4, 62, 63, 66, 71, 75, 82-83, 88, 92, 96, 101-2, 10S, 13031,132,143,169,18S, 193, 207, 226, 254; Murdock, 20, 37; Nebraska, 33-36; New Jersey, 85; New York, 62-63, 85, 168, 226; Oklahoma, 87-88, 197; Prairie Provinces, 102, 104-5, 206-7; Procter et al., 175; Reynoldson, 26, 51, 97, 156, 199, 205, 213, 220, 221; Reynoldson et al., 3, 5, 6, 8, 16, 26, 53-54, 62, 63, 66, 71, 75, 82-83, 85, 88, 92, 93, 97, 101-2, 105, 106, 115, 119, 125, 130-31, 132, 142, 147, 149, 157, 159-60, 165, 167, 169, 182-83, 18S, 193, 202, 20S, 209, 210, 213, 216, 220, 221, 226, 254; Robson and Shanks, 31; Saliers, 67, 71, 79; Saville and Reuss, 3, 86, 168; Schwantes and Pond, 49, 61, 66, 68-69, 92, 97, 100, 110, 167, 220; Shippler, M. M., 91; Sjorgren, O. W., 33-34; Smith and Hurlbut, 12; Smith and Jones, xx, 8, 53, 62-63, 65, 66, 75, 83, 88, 92, 96, 101, 10S, 13031, 143, 168, 170, 185, 186; South Dakota, 53, 96, 101, 124, 175, 177, 226, Starch, 10, 26, 66, 90-91, 96, 152; Stephens, 87, 151, 197; Swiss, 98; Tolley, xi, 89, 185; Tolley and Reynoldson, 85, 1S8; Washbum and Kifer, 86, 89, 91, 93, 101; Washburn and Scudder, 208; Weight and Aylesworth, 27, 170; Young and Collier, 27, 28, 54, 131, 153; Zink et al., 12 tests, 231

273

Tractor (Continued) transportation, 12 types, 3-13, 27, 48; best suited for different purposes, 55-56; ordinary, xviii, 4, 46-47, 91, 135, 158, 226; rubber-tired, 12-13, 44, 52, 229, 233 ; steel wheels, 4-9, 41, 201; three-plow, xii, 3, 106; track-laying, 9-12; two-and-three plow, 24; two-plow, 3, 5-6, 7, 15, 27, 106, 227; with Diesel engines, 106 utilization, xii, xiv, 66, 109-21 value, 233 Tractor Testing Code, 34 Trucks, 127, 159-61; performance compared with horses, 175-77 United States Tractor and Machine Company, 253 University of Nebraska, tractor experiments at, 12-13 Variable charge, defined, 75 Washburn, R. S., and R. S. Kifer, cited, 86, 89, 91, 93, 101 Washbum, R. S., and H. D. Scudder, cited, 208 Watermelons, power requirements of, 150 Wetmore, H. A., 237 Wheat, 55; labor required for, 182; machinery and, 192; power requirements of, 150, 151, 152 Wisconsin Farm Tractor Company, 253 Wright, K. T., ar.d P. E. Aylesworth, cited, 170 Young, E. C., and G. W. Collier, cited, 131, 153 Zink, F. J., cited, 12