Definitional Glossary of Agricultural Terms, Vol-I 9789389795189

Table of contents :
Cover
Half Title
Title
Copyrights
Preface
Foreward
Acknowledgements
Table of contents
Natural Resources Management, Agronomy, Crop Production, Dry Land Agriculture, Agro-meteorology, Sustainable Agriculture, Agro-forestry and Grassland Agriculture, Agricultural Economics, Farm Management, Agro-ecology, Environment, Soil Science, Soil Fertility, Plant Nutrition and Organic Farming

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Volume I

Volume I Dinesh Kumar • Y.S. Shivay Senior Scientists, Division of Agronomy Indian Agricultural Research Institute, New Delhi-110 012 (INDIA)

This volume includes terms related mainly to agronomy, crop production, sustainable agriculture, agro-ecology, environment, soil science, soil fertility, plant nutrition, organic farming, latest concepts in agronomy, agro-forestry and grassland agriculture, agricultural economics, and farm management, etc. It especially explains the new terms in a comprehensive and understandable manner. Very often descriptive text-related terms, synonyms and antonyms are given in addition to the proper definitions to help readers understand the terms in their context and practical usage. Although, it is primarily a definitional glossary of agricultural terms used in India, but various terms used commonly in other developing countries are also included.

978-93-89795-18-9

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Definitional Glossary of Agricultural Terms

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Definitional Glossary of Agricultural Terms Vol. I Natural Resources Management, Agronomy, Crop Production, Dry Land Agriculture, Agro-meteorology, Sustainable Agriculture, Agro-forestry and Grassland Agriculture, Agricultural Economics, Farm Management, Agro-ecology, Environment, Soil Science, Soil Fertility, Plant Nutrition and Organic Farming

Dinesh Kumar • Y.S. Shivay Senior Scientists, Division of Agronomy Indian Agricultural Research Institute,z New Delhi-110 012 (INDIA)

©Copyright 2020 I.K. International Pvt. Ltd., New Delhi-110002. This book may not be duplicated in any way without the express written consent of the publisher, except in the form of brief excerpts or quotations for the purposes of review. The information contained herein is for the personal use of the reader and may not be incorporated in any commercial programs, other books, databases, or any kind of software without written consent of the publisher. Making copies of this book or any portion for any purpose other than your own is a violation of copyright laws. Limits of Liability/disclaimer of Warranty: The author and publisher have used their best efforts in preparing this book. The author make no representation or warranties with respect to the accuracy or completeness of the contents of this book, and specifically disclaim any implied warranties of merchantability or fitness of any particular purpose. There are no warranties which extend beyond the descriptions contained in this paragraph. No warranty may be created or extended by sales representatives or written sales materials. The accuracy and completeness of the information provided herein and the opinions stated herein are not guaranteed or warranted to produce any particulars results, and the advice and strategies contained herein may not be suitable for every individual. Neither Dreamtech Press nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Trademarks: All brand names and product names used in this book are trademarks, registered trademarks, or trade names of their respective holders. Dreamtech Press is not associated with any product or vendor mentioned in this book. ISBN: 978-93-89795-18-9 EISBN: 978-93-89872-96-5

Edition: 2020

v

Preface This definitional glossary provides a descriptive introduction to the key concepts relevant to agriculture. It has been divided into two volumes. Volume I includes terms related to agronomy, crop production, sustainable agriculture, agro-ecology, environment, soil science, soil fertility, plant nutrition, organic farming, latest concepts in agronomy, agro-forestry and grassland agriculture, agricultural economics and farm management, etc. Volume II includes terms related to crop sciences, genetics, biotechnology, plant breeding, plant physiology and biochemistry, plant pathology, plant protection, horticulture, seed science and technology, statistics, internet, library and information sciences, etc. There are also some terms concerning to statistics, library and information science that are commonly useful to agriculture. Although it is primarily a definitional glossary of agricultural terms used in India, some terms in common use in other developing countries are also included. It contains terms used by students, professors, scientists and extension workers. Detailed explanation of various specialised terms and enviromental issues have also have been provided. Important information related to cell biology, agronomy, soils, soil fertility, manures and fertilizers, organic farming and crop residues, etc. have been presented in tabular form in Volume II, in a concise manner. Tables relating to symbols, units of measurements and conversion factors are also provided in Volume II. Sources have been specified for almost all the Tables. Definitions are listed in alphabetical order and consist of the definition and descriptive terms. Many terms feature multiple definitions. These definitions are listed in numerical order (i), (ii), (iii), etc. In addition to the proper definition, descriptive text, related terms, synonyms and antonyms are given to enhance reader’s understanding and its practical usage. Correspondence noting errors, omissions or containing suggestions are welcomed in anticipation of future editions of this glossary.

Dinesh Kumar Y.S. Shivay

Foreword The period of the development of the human race during which began the cultivation of plants marks the dawn of agriculture. There is ample evidence that numerous civilizations, from ancient Sumeria and Babylonia to those that use modern high-intensity, high-input agriculture, have suffered with problems of long-term sustainability. Vedic literature suggests that five basic elements govern the life processes, including plants and animals. These are earth, water, air, fire and other. Therefore, proper and efficient management of these elements would lead to sustainable agriculture and better living conditions for everyone. In this context, need is being increasingly felt to improve and refine the agricultural research, spreading the gained knowledge to the concerned, and of course training the farmers to achive the goal of agricultural sustainability. The current book in two volumes is a commendable work by the authors to spread the available knowledge on the subject. The principal purpose of this glossary is to bring together terms from different subjects of agricultural sciences ranging from agronomy, genetics, plant biotechnology, plant breeding, environmental sciences to agricultural statistics. The multidisciplinary nature of the book and the wide range of subjects covered will provide up-to-date information on all terms relating to broader and newer areas of agricultural sciences. The knowledge gained will help the readers a better understanding. It would serve as a useful reference for professors, teachers, researchers, students, and consultants, engaged in different branches of agricultural sciences. I hope this glossary would be useful to the concerned.

(S.A. Patil) Director Agricultural Research Institute, New Delhi-110012

Acknowledgements The idea to start with the compilation of a glossary covering terms related to new developments in agriculture was suggested by the PG students here at IARI, New Delhi. The encouragement, critical review and valuable suggestions by many people within IARI and from outside have helped to attain the present version of this glossary. Authors are thankful to the PG students, especially Mr. Gulab Singh Yadav, Ramanjit Singh and Ms. Kapila Shekhawat, Division of Agronomy, IARI for checking the errors in typing. We wish to thank Dr I.P.S. Ahlawat, Head, Division of Agronomy and Dr S.A. Patil, Director, Indian Agricultural Research Institute, New Delhi, for their kind suggestions and critical comments for improvement of the manuscript. The encouragement and inspiration rendered by Prof. Rajendra Prasasd, Ex-National Professor (Agronomy) and INSA Honorary Scientist, Division of Agronomy, IARI, New Delhi is duly acknowledged.

Dinesh Kumar Y.S. Shivay

Contents Preface ............................................................................................................................................................. v Foreword ....................................................................................................................................................... vii Acknowledgements ......................................................................................................................................... ix Natural Resources Management, Agronomy, Crop Production, Dry Land Agriculture, Agro-meteorology, Sustainable Agriculture, Agro-forestry and Grassland Agriculture, Agricultural Economics, Farm Management, Agro-ecology, Environment, Soil Science, Soil Fertility, Plant Nutrition and Organic Farming ....................................................................................1-314

A factor

A A factor: It is the computed longtime average annual soil loss carried by runoff from specific field slopes in specified cropping and management systems. It is expressed in the RUSLE model in tons/acre/year. A horizon: The name given to the surface (top) layer of a soil profile. This horizon has more organic matter and dense microbial population hence greatest biological activity than other layers or horizons, such as B horizon and C horizon. It is also referred to as the surface mineral horizon with decomposed organic matter. This is the most important horizon from crop nutrition and microbial activity point of view. As the top soil, it is also the first layer to be lost during soil erosion and its protection is aimed at by various soil conservation measures. AB-DTPA extraction reagent: An acronym for an extraction reagent of 1 M ammonium bicarbonate ( NH4 HCO3) in 0.005 M diethylenetriaminepenta acetic acid ( DTPA) that has a pH of 7.6 and is used for the extraction of phosphorus (P), potassium (K), sodium (Na), iron (Fe), manganese (Mn), and zinc (Zn) from alkaline soils. abiontic enzymes: Enzymes (exclusive of live cells) that are (i) excreted by live cells during growth and division; (ii) attached to cell debris and dead cells; (iii) leaked into soil solution from extant or lyzed cells but whose original functional location was on or within the cell. Synonymous with exoenzymes. abiotic factor: (i). Not biotic i.e., not living: Factors like pH, temperature, moisture etc are abiotic. These factors play a major role in plant nutrition, microbial activity and crop growth. (ii). Physical, chemical and other non-living environmental factors. They are essential for living plants and animals of an ecosystem, providing the essential elements and nutrients that are necessary for growth. The abiotic elements also include the climatic and pedologic components of the ecosystem. ablation till: Loose, permeable till deposited during the final down-wasting of glacial ice. Lenses of crudely sorted sand and gravel are common. abrasion: Breakdown of clods, crusts, and plant material by the impact of particles moved by wind in saltation. The impacting particles may also abrade. Abrasion causes soil aggregates to break down progressively as wind erosion continues.

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absolute humidity: Measurement of atmospheric humidity. In a system of moist air, the ratio of the mass of water vapour present to the volume occupied by the mixture; that is, the density of the water vapour component. Absolute humidity is normally expressed in grams of water vapour in a cubic metre of air. absolute water requirement: Also called consumptive use of water. This is the quantity of water in ha-cm per crop season absorbed by the crop together with the evaporation from the crop producing land. It includes the water used by evapotranspiration and retained in plant body. absolute weed: These are the plants, which are undesirable regardless of time and place. absolute zero: Considered to be the point at which theoretically no molecular activity exists or the temperature at which the volume of a perfect gas vanishes. The value is 0° Kelvin, -273.15° Celsius and -459.67° Fahrenheit. absorption spectroscopy: This is a technique for determining the concentration and structure of a substance by measuring the amound of electromagnetic radiation the sample absorbs at various wavelengths. absorption spectrum (pl. spectra): This is a plot that shows how much radiation a substance absorbs at different wavelengths. Absorption spectra are unique for each element and compound and they are often used as chemical “fingerprints” in analytical chemistry. The spectrum can represented by a plot of either absorbance or transmittance versus wavelength, frequency, or wavenumber. absorption, active: It is movement of ions and water into the plant root because of metabolic processes by the root, frequently against an electrochemical potential gradient. absorption, passive: It is movement of ions and water into the plant root from diffusion along a chemical potential gradient. absorption: It is uptake of matter or energy by a substance. The process by which atoms, molecules, or ions are taken up from the soil solution or soil atmosphere and retained on the surfaces of solids by chemical or physical binding. absorptivity: It is the absorbance of a solution per unit of path length and per unit concentration; a = A/

A

2

A

acaricide

(bc) where a, A, b, and c are the absorptivity, absorbance, path length, and concentration, respectively. Absorptivity varies with wavelength of the incident light.

200 kg N ha-1. It is a small rod shaped, aerobic, gram-negative motile bacteria. It also solubilises insoluble phosphorus. It is recommended for sugarcane.

acaricide: Any chemical agent that kills members of the Order Acarina (mites and ticks).

acetylene reduction assay (ARA): The quantitative method for estimating biological nitrogen fixation through gas chromatography. The enzyme nitrogenase (N-ase), which is responsible for biological N fixation, can reduce the gas acetylene (C2H2) to ethylene (C2H4) as well as dinitrogen (N2) to ammonia (NH3).

acaulospora: It is one of the genera of VA-mycorrhiza. Example: Acaulospora scrobiculata. Acaulospora spores are found in citrus rhizosphere (130-380 spores/100 g soil). accelerated erosion: When soil erosion is in excess of natural rates, usually as a result of anthropogenic activities. access tube: Small diameter tube (typically about 50 millimetres) inserted through the soil root zone to provide passage of a neutron probe to determine the water content of soil at various depths. acclimated microorganism: It refers to a microorganism that is able to adapt to a specified environmental change such as in temperature, soil reaction, oxygen concentration etc. Example: acid tolerant rhizobia, which can survive at low pH where most bacteria cannot. accreditation: Procedure by which an authoritative body gives a formal recognition that a body or person is competent to carry out a specific task. The term is now used for monitoring organically-grown farm produce as well as organic fertilizers. The functions of such accreditation agencies include prescribing packages of practices for organic production in their respective schedule, laying down the production procedure, certification of produce etc. For example IFOAM (International Federation of Organic Agriculture Movement) is an accreditation agency for organic farming and organically-produced farm produce acetic acid bacteria: Bacteria that release acetic acid (CH3COOH). Example: the N-fixing Acetobacter and Acetobacterium. acetic acid: The formula is CH3COOH, HC2H3O2. Ethanoic acid; vinegar acid; methanecarboxylic acid. A simple organic acid that gives vinegar its characteristic odour and flavour. Glacial acetic acid is pure acetic acid. Acetobacter: It (Acetobacter diazotrophicus) is a new N-fixing bacteria found in the roots, stems and leaves of sugarcane with a potential N-fixing capacity of

acetylene-block assay: A technique for demonstrating or estimating denitrification by measuring nitrous oxide (N2O) released from acetylene-treated soil. Acetylene inhibits nitrous oxide reduction to dinitrogen (N2) by denitrifying bacteria. acid detergent fibre (ADF): The fraction of undigestible plant material in forage, usually cellulose fibre coated with lignin. acid equivalent (a.e.): The portion of pesticide that is theoretically converted into acid. acid precipitation: Atmospheric precipitation that is below pH 7 and is often composed of the hydrolyzed by-products from oxidized halogen, nitrogen, and sulphur substances. acid rain: Acid rain is mainly caused by sulphur dioxide, nitrogen oxide and other pollutants mainly cause Acid rain when fossil fuels are burnt. Acid rain rarely falls near the source of the pollutant because smoke, fumes etc can be carried many miles by air currents. The main effects of acid rain are on wildlife. Water in lakes also becomes very clear as fish and microscopic life are killed off. It is thought that acid rain is responsible for the death of some trees, specifically conifers, which gradually lose all their leaves and die. acid soil: A soil with a pH value less than 7.0 hence having more hydrogen (H+) ions than hydroxyl (OH) ions in the soil solution. In humid regions, where rainfall is high, the soluble bases formed in the course of weathering of rocks are leached down and carried away by the drainage waters. The continued leaching of soils results in the replacement of calcium, magnesium, potassium and sodium ions by hydrogen ions and the formation of acid soils with low pH occurs. In acid soils the dissolution of aluminosilicate minerals occur and the aluminium ions thus released increase the acidity owing to hydrolysis. Similarly,

acidity, salt-replaceable humus and hydrous oxides contribute to soil acidity at low pH. Acid soils range from slightly acid (pH 6.1-6.5) to extremely acid (pH below 4.5). Micronutrient availability, except in case of Mo is usually higher in acid soils than in alkaline soils. Very acid soils can be amended with calcitic or dolomitic limestone and calcium-rich industrial by products such as sugar factory press mud, paper mill sludge etc. acid sulphate soil: The acid sulphate soils, also known as cat clays, have a soil pH as low as pH 3.0 when drained. This is caused by the presence of dilute sulphuric acid resulting from sulphide oxidation. Some soils are also salt-affected. They often contain toxic amounts of Fe, Al and sulphate but are generally poor in most major nutrients. Potentially acid sulphate soils occur in tidal swamps. Such soils often produce very low yields, sometimes less than 1 tonne/ha of grain. However, even small amounts of lime, in combination with phosphate rock may increase the yield to 2–3 tonnes/ha. After complete amelioration, which is not easy, these soils can produce yields as high as normal soils. The best way to manage such soils is amelioration with lime, phosphate rock and a general increase in nutrient levels, which requires substantial capital input. However, these soils are generally used in their natural state for growing paddy rice as flooding increases soil reaction. Where the main problem is Fe toxicity, using cultivars with high tolerance to Fe can solve the problem to a certain extent. acid-forming fertilizer: A kind of fertilizer that leaves behind an acidic effect in the soil (reduces soil pH). Mostly such fertilizers, which lack a metallic cation, are acid forming. Their continuous use makes a soil acid (lowers pH) and reduces soil quality and hence productivity. The excess acidity can be neutralized by lime application. This is generally of practical importance in case of nitrogenous fertilizers. Example: ammonium sulphate, ammonium chloride, anhydrous ammonia and urea. acidic cations: Cations that, on being added to water, undergo hydrolysis resulting in an acidic solution. Hydrated acidic cations donate protons to water to form hydronium ions (H3O+) and thus in aqueous solutions are acids. Examples in soils include Al3+ and Fe3+. acidification: It is a process of becoming more acid. pH 7 is neutral, above this is alkaline below pH 6 is

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acidic. i.e. acidification of the soil. The reduction in pH of the soil is generally brought about by removal of cations (mainly Ca2+ and Mg2+) by leaching or removal in the crop. acidity (soil): This is a chemical condition caused by acidic environment (excess of H +). Acidity has adverse effect on the establishment of inoculated bacteria especially in very acid soils associated with the toxicity of aluminium and manganese or calcium deficiency. Soils become acid when basic elements, such as calcium, magnesium, sodium, and potassium held by soil colloids are replaced by hydrogen ions. Soils formed under conditions of high annual rainfall are more acid than are soils formed under more arid conditions. Soils formed under low rainfall conditions tend to be generally basic with soil pH readings above 7.0. However, intensive farming over a number of years with nitrogen fertilizers or manures can result in soil acidification. Water (H2O) combines with carbon dioxide (CO2) to form a weak acid — carbonic acid (H2CO3). The weak acid ionizes, releasing hydrogen (H + ) and bicarbonate (HCO3 - ). The released hydrogen ions replace the calcium ions held by soil colloids, causing the soil to become acid. The displaced calcium (Ca2+) ions combine with the bicarbonate ions to form calcium bicarbonate, which, being soluble, is leached from the soil. The net effect is increased soil acidity. acidity potential: The amount of exchangeable hydrogen ion in a soil that can be rendered free or active in the soil solution by cation exchange. Usually expressed in milli equivalents per unit mass of soil. acidity, active: The activity of hydrogen ion in the aqueous phase of a soil expressed as a pH value. acidity, exchange: The acidity of a soil that can be neutralized by lime or a solution buffered in the range of 7 to 8. acidity, free: The titratable acidity in the aqueous phase of a soil. acidity, residual: Soil acidity that is neutralized by lime or a buffered salt solution to raise the pH to a specified value (usually 7.0 or 8.0) but which cannot be replaced by an unbuffered salt solution. It can be calculated by subtraction of salt replaceable acidity from total acidity. acidity, salt-replaceable: The aluminium and hydrogen that can be replaced from an acid soil by an unbuffered salt solution such as KCl or NaCl.

A

4

A

acidity, total

acidity, total: The total acidity including residual and exchangeable acidity. Often it is calculated by subtraction of exchangeable bases from the cation exchange capacity determined by ammonium exchange at pH 7.0. It can be determined directly using pH buffer-salt mixtures (e.g. BaCl 2 plus triethanolamine, pH 8.0 or 8.2) and titrating the basicity neutralized after reaction with a soil.

been improved for use on land. On the average, nutrient content of activated sewage sludge is 5.8% N, 3.2% P2O5 and 0.6% K2O. It also contains lesser and variable amounts of secondary and micronutrients and toxic heavy metals. Care has therefore to be taken while deciding the optimum application rates considering its composition. A potential organic fertilizer.

acidophile: Term referring to acid loving. An organism that grows well under acidic conditions. Example: Acetobacter diazotrophicus.

activator: A substance that can accelerate (speed up) a process, usually of decomposition. Trichurus spiralis, Paeciliomyces fusisporus, and Trichoderma viride are used as compost activators (accelerators) as the inoculation of compost piles with such organisms speeds up the process and cuts down the compost preparation time.

acidulant: It is a substance added to food or beverages to lower pH and to impart a tart, acid taste. Phosphoric acid is an acidulant added to cola drinks. acidulation: It is a process of treating a fertilizer source with an acid. The most common process is treatment of phosphate rock with an acid (or mixture of acids) such as sulphuric, nitric, or phosphoric acid. acre-foot (acre-ft): The volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic metres. actinomycetes: A group of microorganisms, intermediate between bacteria and true fungi, that usually produces a characteristic branched mycelium. These organisms are responsible for the earthy smell of compost. actinorhizal plants: Plants, which are nodulated by Frankia - a nitrogen-fixing actinomycete. The resulting nitrogen-fixation is similar to that by Rhizobium in symbiosis with legumes. Example: Alnus, Casuarina etc. activated charcoal: Charcoal, which has been treated to remove impurities. Activation carried out by heating charcoal under partial aeration. Used in chemical analysis. activated coal: This is the most commonly used adsorption medium, produced by heating carbonaceous substances or cellulose bases in the absence of air. It has a very porous structure and is commonly used to remove organic matter and dissolved gases from water. Its appearance is similar to coal or peat. Available in granular, powder or block form; in powder form it has the highest adsorption capacity. activated sewage sludge: It is biologically active sewage sludge which has been obtained by repeated exposure of sewage to atmospheric oxygen, thus facilitating the growth of aerobic bacteria and other unicellular micro-organisms and in the process has

active ingredient (a.i.): The potent portion of a compound (such as fertilizer, insecticide, fungicide or herbicide applied on the soil or plant) used as basis to estimate the chemical effect. Useful for comparing the strength or toxicity of chemicals. activity index (Al): Activity index is used by the Association of Official Analytical Chemists (AOAC) to evaluate the solubility of urea formaldehyde compounds: AI =

%CWIN − %HWIN X100 %CWIN

Where CWIN, nitrogen insoluble in cold water (25° C); and HWIN, nitrogen insoluble in hot water (100°C). actual evapotranspiration: It is an average value, which represents the actual rate of water uptake by the plant. It is determined by the level of available water in the soil. Evapotranspiration comprises the simultaneous movement of water from the soil and vegetation into atmosphere through evaporation (E) and transpiration (T). ad libitum feeding: Where animals are permitted to eat daily as much as they desire. adaptive research: Research conducted to validate, modify and/or calibrate a new technology to specific soil, climate, socioeconomic, or environmental characteristics of a given area. additive (fertilizer): Material incorporated in a fertilizer- (i) to improve its physical performance/ condition, e.g. in storage or spreading characteristics, (ii) to provide a minor nutrient, e.g. boron, (c) to provide a non-nutrient biological action, e.g. pesticides or growth regulators.

aeration, soil additive series: In intercropping, introduction of another plant species without reducing the population of the first species from the optimum. adhesion (water): It occurs when water molecules are attracted to other types of molecules, such as glass, soil, metal or plant leaves, since the other surfaces also have charges. Adhesion forces are stronger than cohesion forces. The water beads on the leaves because the leaves have a waxy coating, which weakens the adhesive forces of the water molecules toward the leaf surface. The droplets hang together due to cohesive forces of the water molecules for each other, rather than spreading out into a thin film of water. If we place water in a pan and then put a capillary tube in the water, water will rise inside the tube. The smaller the tube, the more adhesive forces are in play and the higher the water rises. In big tubes, the cohesive forces pull the water down into the tube and keep it from rising. adhesives: A group of sticky substances used as glue. Stickers such as wall paper glue (5%), gum arabic (4%), carboxy methyl cellulose (4%), honey (10%), gur (unrefined sugar) or sugar (10%), powdered milk (10%) and jaggery etc. are used as adhesives for the bacterial biofertilizers to stick onto the seed and in addition also serve as food for the bacteria. adjuvant: Substance added to a formulated pesticide product to act as a wetting or spreading agent, sticker, penetrant, or emulsifier in order to enhance the physical characteristics of the product. adsali sugarcane: Sugarcane, which takes 18 months for harvesting, usually planted in June-July. adsorption coefficient (Koc): It is a measure of a material’s tendency to adsorb to soil particles. High Koc values indicate a tendency for the material to be adsorbed by soil particles rather than remain dissolved in the soil solution. Strongly adsorbed molecules will not leach or move unless the soil particle to which they are adsorbed moves (as in erosion). Koc values of less than 500 indicate little or no adsorption and a potential for leaching. Koc = (conc. adsorbed/conc. dissolved)/(% organic carbon in the soil). adsorption complex: Collection of various organic and inorganic substances in soil that are capable of adsorbing ions and molecules. adsorption isotherm: A graph of the quantity of a given chemical species bound to an adsorption

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complex, at fixed temperature, as a function of the concentration of the species in a solution that is in equilibrium with the complex. Called an isotherm only because adsorption experiments are done at constant temperature. adsorption: (i). The taking up/uptake of molecules or ions at a surface, including exchangeable cations and anions on soil particles. (ii). The sticking of a liquid, or gaseous or dissolved substance to a solid, resulting in higher concentration of the substance. advance time (irrigation): The time it takes the first water applied to a dry irrigation furrow to travel the length of the furrow. In other words it is the portion of the total irrigation time during which water advances in over land flow surface from the upper end of the field to the lower end of the field. The time elapsed during this phase is called advance time. advection fog: Fog generated by winds that contrast in temperature with the Earth’s surface. Warm air advection can produce fog through contact cooling with a cold surface. advection: Advection involves the transfer of heat energy by means of horizontal mass motions through a medium. advective energy: The energy developed from horizontal heterogeneity in climatic parameters or the energy brought in an area through horizontal movement of winds. (It is an important source of energy if winds are coming from hot and dry adjacent areas, especially in tropical hot summers, which results in greater evapo-transpiration than normally due to solar energy). aeolian landform: Is a landform formed from the erosion or deposition of weathered surface materials by wind. This includes landforms with some of the following geomorphic features: sand dunes, deflation hollows, and desert pavement. Alternative spelling eolian landform. aerate: To allow or promote exchange of soil gases with atmospheric gases. aeration porosity: The proportion of the bulk volume of the soil that is filled with air when the moisture tension is at some specified value. The tension is usually specified in the range 40 to 100 cm of water. aeration, soil: The process by which air in the soil is replaced by air from the atmosphere. In a well-aerated soil, the soil air is very similar in composition to the

A

6

A

aerial deposition

atmosphere above the soil. Poorly aerated soils usually contain a much higher content of CO2 and a lower content of O2 than the atmosphere above the soil. The rate of aeration depends largely on the volume and continuity of air-filled pores within the soil. aerial deposition: Some nutrients are supplied in small quantities to the soil surface through aerial deposition. These include nitrates in rainwater, ammonia as a gas or dissolved in rainwater, sulphur in acid rain, salts and chlorine in marine spray and calcium in the form of dust. aerial spraying: Application of pesticide or fertilizer in the form of spray by using aero plane or helicopter, with the objective of covering vast area in a short time. aerobic composting: The process of composting organic wastes of plant and animal origin such as animal shed bedding, sweeping, urine, plant waste, cattle dung etc in the presence of air. aerobic digestion: The partial biological decomposition of suspended organic matter in wastewater or sewage in aerated conditions. aerobic: (i). Having molecular oxygen as a part of the environment. (ii). Growing only in the presence of molecular oxygen, such as aerobic organisms. (iii). Occurring only in the presence of molecular oxygen (said of chemical or biochemical processes such as aerobic decomposition). aeroponics: A technique in growing plants wherein the plants derive their nutrients and water from a mist of air and aqueous solution that comes in contact with the roots. aerosol: Particulate matter, solid or liquid, larger than a molecule but small enough to remain suspended in the atmosphere. Natural sources include salt particles from sea spray, dust and clay particles as a result of weathering of rocks, both of which are carried upward by the wind. Aerosols can also originate as a result of human activities and are often considered pollutants. Aerosols are important in the atmosphere as nuclei for the condensation of water droplets and ice crystals, as participants in various chemical cycles, and as absorbers and scatters of solar radiation, thereby influencing the radiation budget of the Earth’s climate system. afforestation: (i). Conversion of bare land into forestland by planting of forest trees. (ii). The

planting of a forest crop on land that has not previously, or not recently, carried a forest crop. aflatoxin: Aflatoxin is a naturally occurring mycotoxin produced by two types of mold: Aspergillus flavus and Aspergillus parasiticus. Both species are common and widespread in nature, but A. flavus is more likely to infect grain, cotton seed, and peanuts grown under stressful conditions such as drought. Favourable conditions for mold growth include high moisture content and high temperature. At least 13 different types of aflatoxin are produced in nature with aflatoxin B1 considered as the most toxic. after-cultivation: Harrowing, rolling, tilling and other cultivations carried out in a field after the crop has emerged. agar agar: A dried gelatin like mucilaginous substance used as solidifying agent to form the base for solid and semi solid culture media for bacteria. It is extracted from Ceylon moss (Gelidium corneum), red alga (Rhodophyceae). Chemically it is a kind of polysaccharide. It solidifies at about 38°C and melts at about 100ºC. Also known as ‘agar’. agenda 2000: It is a Common Agricultural Policy (CAP) reform package proposed by the European Commission in 1998. After a number of modifications, the European Union Heads of State agreed to a package of reforms in March 1999. agenda 21: Agenda 21 is the plan of action to achieve sustainable development that was adopted by the world leaders at the United Nations Conference on Environment and Development held in Rio de Janeiro, Brazil, in June 1992. aggregate demand analysis: This type of economic analysis takes place at the level of a region or a country. It gives useful information and data of total demand for that area and of the important components that create that demand. It can be extremely useful for studying government policies. However, it does not consider differences among different groups within a society and generally presents an incomplete picture of the welfare of the population. aggregate stability: It is a measure of the stability of soil structure and soil tilth. Aggregate stability refers to the ability of soil aggregates to resist disruption when outside forces (usually associated with water) are applied. Aggregates are conglomerates of clay, silt, and sand particles that are held together by

agricultural economics physical and chemical forces. The bonds that hold these particles together can be broken by applying energy to the soil, for example, by shaking aggregates in water. A common method of determining aggregate stability is to place aggregates on a sieve with uniform openings and move the sieve up and down in a water bath. If a lot of soil passes through the sieve, the aggregate stability is low, while it is high if most soil remains on top of the sieve. Tillage destroys aggregates. Increasing soil organic matter content is the best method to increase aggregate stability. Crop rotations and crop mixtures can help to improve the aggregation of soils. Crops with extensive, fine root systems such as grasses and cereals stimulate aggregate stability in the long term. Crops with easily decomposed residue stimulate aggregate stability in the short term, because bacteria that feast on the residue produce polysaccharides that act as glue holding aggregates together. Amendments (such as manure or sewage sludge) that stimulate biological activity will help improve aggregate stability. aggregate: A group of primary soil particles that cohere to each other more strongly than to other surrounding particles. Soil aggregates are groups of soil particles that bind to each other more strongly than to adjacent particles. The space between the aggregates provides pore space for retention and exchange of air and water. aggregation: The process whereby primary soil particles (sand, silt, clay) are bound together, usually by natural forces and substances derived from root exudates and microbial activity. Soil aggregates are arranged to form soil peds, units of soil structure, classified by size, shape (platy, prismatic, columnar, angular, subangular, blocky, granular…) and grade (single-grain, massive, weak, moderate, strong). From an agronomical point of view, the most important soil aggregates are in range 3 – 1 mm. aggressivity: It gives a simple measure of how much the relative yield increase in species ‘a’ is greater than that for species ‘b’ in an intercropping system and can be expressed as Aab: Aab =

Yab Yba − Yaa Zab Ybb Zba

Where, Yaa = Pure stand yield of species a Yab = Mixture yield of species a in combination with b

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Yba = Mixture yield of species b in combination with a Ybb = Pure stand yield of species b Zab = Sown proportion of species a in mixture with b Zba = Sown proportion of species b in mixture with a agrarian policy: A policy concerned with the land or landed properties. agrarian system: A historically constituted and durable mode of exploitation of the environment; a technical system adapted to the bioclimatic conditions of a given area and which complies with its social conditions and needs at that moment. agribusiness: (i). Agriculturally related businesses that supply farm inputs (such as fertilizer or equipment) or are involved in the marketing of farm products (such as warehouses, processors, wholesalers, transporters, and retailers). (ii). The combination of the producing operations of a farm, the manufacture and distribution of farm equipment and supplies and the processing, storage, and distribution of farm commodities. agric horizon: A mineral soil horizon in which clay, silt and humus derived from an overlying cultivated and fertilized layer have accumulated. The wormholes and illuvial clay, silt and humus, occupy at least 5% of the horizon by volume. The illuvial clay and humus occur as horizontal lamellae or fibres, or as coatings on ped surfaces or in wormholes. agricultural area: Land used primarily for the production or collection of farm commodities. According to the land uses a distinction is made between arable land, land under protective cover, land under permanent crops in open air, land under permanent meadows and pastures both naturally grown or cultivated. agricultural climatology: Climatology as applied to the effect of climate on crops. It includes especially the length of the growing period, the relation of growth rate and crop yields to the various climatic factors and the optimum and limiting climates for any given crop, the value of irrigation, and the effect of climatic and weather conditions on the development and spread of crop diseases . agricultural economics: An applied social science that deals with the production, distribution, and consumption of agricultural or farming goods and services.

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agricultural holding (for economic accounts)

agricultural holding (for economic accounts): An agricultural holding is the economic unit under a single management engaged in agricultural production activities. The unit may also be engaged in nonagricultural activities so that this concept should not be interpreted too strictly; the aim is rather to value the final production of all agricultural products. agricultural holding: Economic unit of agricultural production under single management comprising all livestock kept and all land used wholly or partly for agricultural production purposes, without regard to title, legal form or size. agricultural liming material: Material containing oxides, hydroxides and/or carbonates of calcium and/ or magnesium, used for neutralizing the acidity of the soil and provide calcium and magnesium as elements for the growth of plants. Their usage is referred to as liming. agricultural mechanics: The segment of the agriculture industry dealing with the selection, construction, operation, maintenance and repair or use of agricultural power, agricultural machinery and equipment, structures and utilities, and soil and water management practices. agricultural meteorology (=agrometeorology): This is concerned with the interactions between meteorological and hydrological factors, on the one hand, and agriculture in the widest sense, including horticulture, animal husbandry and forestry, on the other hand. agricultural operation: The management and use of farming resources for the production of crops, livestock or poultry. agricultural policy: The General principles by which a government is guided in its management of matters pertaining to, or dealing with the science or art of cultivating soil, harvesting crops, and raising livestock. agricultural production system: The whole structured set of plants, animals, and activities selected by a farmer for his production unit to achieve its goals. It is a global system that is finalized by farmer socioeconomic objectives and related management strategies. agricultural production: Measured in total output of a crop. agricultural region: Any geographical area in which there is a clearly defined and predominant agricultural

structure producing broadly similar types of farming, such as the Indo-Gangetic plains, Mediterranean region, the prairie provinces of Canada and areas of wet-rice cultivation in Southeast Asia. The delimitation of agricultural regions is closely linked to the classification of Farming Systems. agricultural system: A system with agricultural outputs and containing all the major components. agricultural water managed area: It is the sum of total land under irrigation (full or partial control irrigation-equipped, including equipped lowlands) and other water managed areas for agriculture-spate irrigation areas, flood recession cropping areas, (nonequipped) cultivated lowlands. It does not include rainwater harvesting areas (rainwater harvesting contribute to water gathering for some of the water managed areas). agriculture drainage water: It is the water withdrawn for agriculture but not consumed and returned. It does not go through special treatment and therefore should be distinguished from the wastewater reused. It may be an important water source for crop cultivation. agriculture: A broad class of resource uses which includes all forms of land use for the production of biological (biotic) products - whether animal or plant. Fundamental basis for agriculture is the miraculous process of photosynthesis, the many useful products synthesized by it and the fact that plants and animals (including humans) by and large have a common list of essential nutrients. Nature has endowed the soils with these nutrients, which support much of agricultural activity. The science of agriculture and its application includes many branches such as agronomy, plant breeding, soil science, horticulture etc. In addition, being an applied science, it interacts with most of the physical and biological sciences. Agriculture is now predominantly dependent on external nutrient additions to supplement soil fertility. agri-food industry: Industry dealing with the production, processing, and supply of agricultural food products. agrobacterium: A type of soil bacteria, which are associated with Rhizobium but are also a cause of confusion. While Rhizobium can form root nodules in legumes, Agrobacterium cannot do so. agrobiology: A phase of the study of agronomy dealing with the relationship of yield to the quantity of an added or available fertilizer element.

agronomic efficiency agro-chemical: General term for any chemical used in agriculture/horticulture for enhancing crop production. It includes mineral fertilizers, pesticides, herbicides, fungicides, plant growth regulators, hormones, etc. In practice however, the term is generally used for materials other than mineral fertilizers and soil amendments. agroclimatic regions: The grouping of different physical areas within the country into broadly homogeneous zones based on climatic and edaphic factors. agroclimatic zone: A land unit defined in terms of major climate and growing period, which is climatically the homogeneous response of a crop or a farming system. agroclimatic: Relating to the relationship between crop adaptation and climate. agroclimatology: Study of those aspects of climate, which are relevant to the problems of agriculture. agro-ecological cell (AEC): An area or point with a unique combination of land, soil and climate characteristics. The agroecological cell is the basic processing unit for physical analysis in an AEZ (agroecological zoning) study.

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factors into the analysis of food production systems and to use this knowledge to improve these systems, taking into account the needs of both the ecosystem as a whole and the people within it. agro-economic zones: Zones which are defined in terms of common features from an agricultural point of view. For different purposes these features will differ but may involve such dimensions as climate, soil resources, land use, ethnic groupings and market access . agroeconomics: The economics of agriculture. agroecosystem (=agricultural ecosystem): (i). The collection of physical, environmental, economic and social factors that affect a cropping enterprise. (ii). It is composed of the total complex of the crops or animals in an area together with overall environment and as modified by management practices. agroforestry: Agroforestry is a collective name for land-use systems and technologies where woody perennials (trees, shrubs, palms, bamboos, etc.) are deliberately used on the same land management unit as agricultural crops and/or animals, in some form of spatial arrangement or temporal sequence. In agroforestry systems there are both ecological and economic interactions between the different components.

agroecological zone: (i). A land resource mapping unit, defined in terms of climate, landform and soils, and/or land cover, and having a specific range of potentials and constraints for land use. Essential elements in defining an agro-ecological zone are the growing period, the temperature regime and the soil units. (ii). A major area of land that is broadly homogeneous in climatic and edaphic factors, but not necessarily contiguous, where a specific crop exhibits roughly the same biological expression. (iii). Zones of similar agricultural performance as defined by soil and climate.

agrology: The study of applied phases of soil science and soil management.

agro-ecological zoning (AEZ): The division of an area of land into smaller units, which have similar characteristics related to land suitability, potential production and environmental impact.

agronomic characters: Plant characters related to crop production usually observed during plant growth; e.g., height, maturity, tiller number, panicle size, yield and quality factors.

agroecology: (i). The study of the interrelationships of living organisms with each other and with their environment in an agricultural system. (ii). The use of ecological concepts and principles to study, design, and manage agricultural systems. Agroecology seeks to evaluate the full effect of system inputs and outputs by integrating cultural and environmental

agronomic efficiency: Denotes the units of additional crop produced per unit of input (nutrient) added externally. Example: kg grain/kg of a nutrient (macro or micro) added. Agronomic efficiency has a direct bearing on better utilization of applied nutrients, the profitability of their usage and minimization of nutrient losses.

agrohydrology: The science dealing with the distribution and movement of rainfall and/or irrigation water and soil solution to and from the root zone in agricultural land, and with the distribution and movement of irrigation and surface water in conveyance systems on agricultural land. agroindustry: Industry dealing with the supply, processing and distribution of farm products.

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agronomic rate

agronomic rate: The rate at which fertilizers, organic wastes or other amendments can be added to soils for optimum plant growth. agronomy: (i). Science of agriculture that deals with all aspects of field crop production and soil management. (ii). A branch of agriculture dealing with all aspects of tillage, crop production and soil management including nutrient management. Derived from the Greek word “agros” meaning fields and “nomos” meaning management. agropastoral system: A land-use system in which crops and livestock (but not trees) are the only components. agrosilvicultural system: An agroforestry system for the concurrent production of agricultural crops (including woody perennial crops) and forest crops. The forest crops serve in either a productive or a service role. Woody perennial and agricultural crops are chosen first for their productive capacity. agrosilvipastoral system: Any agroforestry system that includes trees or shrubs and herbaceous food crops and pastures and animals. agrostology: A branch of science which deals with the study of grasses, their classification, management and utilization. agrotain: Agrotain (NBPT) is a product that inhibits conversion of urea to ammonium carbonate, thereby reducing the potential for ammonia volatilization from urea materials, including UAN solutions. Like N-Serve , it might be viewed as an insurance policy that will reduce potential nitrogen losses in seasons when cultivation or rain does not incorporate the urea into the soil soon after application. It is most useful when urea or UAN are applied without incorporation to the surface of fields with high levels of crop residue, such as in no-till situations, or fields with high pH levels at the surface. agroterrorism: The deliberate introduction of an animal or plant disease with the goal of generating fear, causing economic losses, and/or undermining stability. Agroterrorism is a subset of the more general issue of bioterrorism. An agroterrorism event would affect the production agriculture sector economically in terms of plant and animal health, and affect supply and demand. Humans could be at risk in terms of food safety or public health, especially if the chosen disease is transmissible to humans (zoonotic).

ahu rice: An early rice similar to “Aus”; grown in Assam, India. air (=aerial) photographs: Photographs of the land surface taken from aircraft, usually at a vertical angle, normally at scales of from 1:50000 to 1:5000. For interpretation, air photographs are viewed stereoscopically to give a three-dimensional impression. Landforms, vegetation, land use and some infrastructure (especially roads and tracks) can be directly seen on air photographs, while soil properties, geology and other land properties require indirect interpretation and administrative boundaries cannot be seen. Air photographs can also be used as base maps for presentation of a land-use plan. Air photographs may be panchromatic (black and white), colour (true colour) or false colour. air (-filled) porosity: The fraction of the bulk volume of soil that is filled with air at any given time or under a given condition, such as a specified soilwater content or soil-water matric potential. air dry: (i). The state of dryness at equilibrium with the water content in the surrounding atmosphere. The actual water content will depend upon the relative humidity and temperature of the surrounding atmosphere. (ii). To allow to reach equilibrium in water content with the surrounding atmosphere. air entry value: The value of water content or potential at which air first enters a porous media. air mass: Large body of air, often hundreds or thousands of miles across, containing air of a similar temperature and humidity. Sometimes the differences between air masses are hardly noticeable, but if colliding air masses have very different temperatures and humidity values, storms can erupt. air pollution: One or more chemicals or substances in high enough concentrations in the air to harm humans, other animals, vegetation, or materials. Such chemicals or physical conditions (such as excess heat or noise) are called air pollutants. akiochi soil: Soil with an imbalance of nutrients associated with hydrogen sulphide toxicity. These are flooded soils where hydrogen sulphide is formed due to sulphate reduction and anaerobic decomposition of organic matter. albedo: The fraction of the total solar radiation incident on a body that is reflected by it. Albedo can be expressed as either a percentage or a fraction of 1. Snow covered areas have a high albedo (up to about

alkali spreading value (rice) 0.9 or 90%) due to their white colour, while vegetation has a low albedo (generally about 0.1 or 10%) due to the dark colour and light absorbed for photosynthesis. Clouds have an intermediate albedo and are the most important contributor to the Earth’s albedo. The Earth’s aggregate albedo is approximately 0.3. It is measured with albedometer. albic horizon: A mineral soil horizon from which clay and free iron oxides have been removed or in which the oxides have been segregated to the extent that the colour of the horizon is determined primarily by the colour of the primary sand and silt particles rather than by coatings on these particles. albolls: Mollisols that have an albic horizon immediately below the mollic epipedon. These soils have an argillic or natric horizon and mottles, iron-manganese concretions, or both, within the albic, argillic or natric horizon. (A suborder in the U.S. system of soil taxonomy).

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bottom, producing increased quantities of chemicals and toxic gases. All these changes further accelerate the eutrophication (aging) of the aquatic ecosystem. algorithm of biofertilizer production: Refers to the series of operations involved in biofertilizer production. The steps are: collection of suitable strain, its inoculation in a particular medium, incubation for growth, incorporation into fermentor for multiplication and curing (2-3 days), mixing the broth with carrier, packing, and despatch. algorithm: A mathematical relation between an observed quantity and a variable used in a step-bystep mathematical process to calculate a quantity. In the context of remote sensing, algorithms generally specify how to determine higher-level data products from lower-level source data. For example, algorithms prescribe how atmospheric temperature and moisture profiles are determined from a set of radiation observations originally sensed by satellite sounding instruments.

aleurone layer: (i). The peripheral layer of endosperm of the grain beneath the seed coat, which envelops the endosperm and contains oil and protein. (ii). It is a layer of high-protein cells surrounding the storage cells of the endosperm. Its function is to secrete hydrolytic enzymes for digesting food reserves in the endosperm.

alien weeds: When a weed is allowed to move from the place of its origin to a new area, and it establishes itself there, it becomes an introduced weed in its new environment. Such weeds are known as alien weeds or anthrophytes.

alfisols: Mineral soils that have umbric or ochric epipedons, argillic horizons, and that hold water at NO-3 > Cl-.

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anion

anion: A negatively charged ion. Example: nitrate (NO3), sulphate (SO 42–), borate [B(OH) 4–], molybdate (MoO42), chloride (Cl–). During electrolysis, it travels to the anode (positive electrode). annual crops: Crop plants that complete their life cycles within a season or year such as rice, wheat, maize, mustard and tobacco. They produce a crop of seed and die. Some of these crop plants may produce tillers. If such rooted tillers are separated from the main shoot and planted, each tiller will survive that season as a new plant, but will not live until another season. annual plants: Plant species that complete their lifecycle within 12 months from the date of germination. antagonism: In plant nutrition, the interference of one element with the absorption or utilization of other nutrient by plants. antagonism: It is the phenomenon in which one element or substance inhibits or reduces the uptake, assimilation or performance of the other. It is not mutually beneficial or performance-enhancing. Common in soil-plant systems and largely a fall-out of nutrient imbalance. Example: P-Zn antagonism. Nutrients exhibiting antagonism are referred to as antagonistic. antagonistic symbiosis: A symbiotic association which is destructive to one of the symbionts or partners involved in the association. anthropogenic: Human made. In the context of greenhouse gases, emissions that are produced as a result of human activities. antibiosis: The antagonistic association between two organisms producing detrimental effects on one of them. It could also mean an association between one organism and a metabolic product of another. anti-caking agent: A Substance used as surface treatment for granular fertilizers to prevent caking or lump formation on storage particularly under humid conditions or on prolonged storage. Used mostly for fertilizers containing major nutrients. Example: talc, chalk, kaolin, oil, clay. anticline: Layers of rock folded into the shape of an arch. The youngest rock layers are on the outer layer of the arch, and the oldest layers are at the core of the fold. Anticlines with reservoir-quality rocks in their core and impermeable rocks in the outer layers of the fold are excellent traps for oil and gas and are

therefore important in petroleum exploration and extraction. The opposite of a syncline. anticyclone: An atmospheric pressure system consisting of an area of high pressure and outward circular surface wind flow. In the Northern Hemisphere winds from an anticyclone blow clockwise, while in Southern Hemisphere systems blow counterclockwise or anticlockwise. anti-quality constituents (forages): The toxic substances present in forage plants which may either cause direct metabolic damage to the animal or interfere with some phase of digestive utilization are referred to as anti-quality constituents. The antiquality constituents of some forage species are as follows: Castrogens (Subterranean clover, red clover, white clover), Coumarins (Sweet clover-Melilotus spp.), Saponins (Lucerne/alfalfa, ladino clover, bur clover, strawberry clover, trefoil), Alkaloids (Phalaris, Lupins, Desmodium, Lespedeza, Crotalaria), Hydrocyanic acid/HCN/ prussic acid / cyanigenetic glucosides (Sorghum spp., Trifolium repens, Lotus spp., Poa acquatica, Zieria laevigata, Phyllanthus qastroemmii, Cynodon plectostachyus, Pteridium acqullinum), Nitrate (Oat, paragrass), Oxalic acid (Napier grass, pearlmillet), Mimosine (subabool- Leucaena leucocephala), Bloat-producing constituents-plant cytoplasmic protein (Trifolium spp., white clover), and Tannins (Shrub and tree spp.). apatite: Common name of the major P-bearing compound in rock phosphates (used as raw material in the manufacture of phosphate fertilizers). General formula: Ca10(PO4, CO3)6 (F, OH, Cl)2. Depending upon the dominance of F, Cl or OH in the apatite crystal structure, it is known as fluorapatite, chlorapatite or hydroxyapatite. apedal soil material: Soil materials without peds, i.e. structureless. apparent nutrient recovery (ANR): A conventional measure of the proportion of applied nutrient recovered in the crop biomass. If a crop absorbs 10 kg P/ha without P application and 16 kg P/ha when 30 kg P/ha is applied, then the apparent recovery of P is 20% {(16-10)x100/30}. application rate: (i). (irrigation) Rate at which water is applied per unit area; usually in mm per hour, (ii). Weight or volume of a fertilizer, soil amendment, or pesticide applied per unit area.

aquox application rate: The amount of fertilizer, insecticide, or herbicide applied per unit area or volume in experiments or commercial production. applied research: Research in which results can be used immediately by the farmer and can be applied to the peculiar problems of a country or a region. appropriate technology: It is a technology that may be suitable or proper in the context of a particular community, region, or country. It must be economically viable, technologically feasible and should fit in the socio-economic fabric of the local communities. approved fertilizer/fertilizer grade: A fertilizer/ fertilizer grade, which is recognized through fertilizer legislation and listed in the fertilizer legislation documents of a country. Example: fertilizers, which are listed in the Fertilizer Control Order (FCO) and approved for production or sale in India. aqua regia: A mixture of nitric and hydrochloric acids, usually 1:3 or 1:4 parts HNO3 to HCl, used to dissolve gold. aquaculture: Aquaculture is the farming of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. Farming implies some sort of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators. aqualfs: Alfisols that are saturated with water for periods long enough to limit their use for most crops other than pasture or woodland unless they are artificially drained. Aqualfs have mottles, ironmanganese concretions or gray colours immediately below the A1 or Ap horizons and gray colours in the argillic horizon. (A suborder in the U.S. system of soil taxonomy.) aquasilvicultural system: An agroforestry system that combines trees with the raising of aquatic animals. aquatic plant: A plant that grows and develops in standing water and provides sufficient aeration to the parts under water. aquents: Entisols that are saturated with water for periods long enough to limit their use for most crops other than pasture unless they are artificially drained. Aquents have low chromas or distinct mottles within 50 cm of the surface, or are saturated with water at all times.

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aqueous ammonia: A solution containing water and ammonia in any proportion, usually qualified by a reference to ammonia vapour pressure. Aqua ammonia for example has a pressure of less than 0.7 kg/cm2 (10 lb/in2). Commercial grades commonly contain 20-25% nitrogen. It is used either for direct application to the soil or for preparation of ammoniated superphosphate. aquerts: Vertisols that are saturated with water for periods long enough to limit their use for most crops other than pasture and woodland unless they are artificially drained. Aquerts have in one or more horizons between 40 and 50 cm from the surface, aquic conditions for some time in most years and chromas of two or less in 50 percent of the pedon or evidence of active ferrous iron. aquic conditions: Continuous or periodic saturation and reduction. The presence of aquic conditions is indicated by redoximorphic features and can be verified by measurement of saturation and reduction. aquic moisture regime: A reducing moisture regime in a soil that is virtually free of dissolved oxygen because it is saturated by ground water or by water of the capillary fringe. aquic: A mostly reducing soil moisture regime nearly free of dissolved oxygen due to saturation by groundwater or its capillary fringe and occurring at periods when the soil temperature at 50 cm below the surface is >5°C. aquiclude: A sediment body, rock layer, or soil horizon that is incapable of transmitting significant quantities of water under ordinary hydraulic gradients. aquifer: Rock formations that store groundwater. A saturated, permeable geologic unit of sediment or rock that can transmit significant quantities of water under hydraulic gradients. aquitard: A body of rock or sediment that retards but does not prevent the flow of water to or from an adjacent aquifer. It does not readily yield water to wells or springs but may serve as a storage unit for groundwater. aquorizem: Soil characterized by a distinct accumulation horizon of iron oxide and manganese oxide below the traffic pan, formed as result of wetland rice cultivation. aquox: Oxisols that have continuous plinthite near the surface, or that are saturated with water sometime

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arable land

during the year if not artificially drained. Aquox have either a histic epipedon, or mottles or colours indicative of poor drainage within the oxic horizon or both. arable land: Land which is ploughed, and on which crops are cultivated; agriculture based on the production of field crops, such as sorghum, millet, maize and vegetables. Arable land includes all land used in most years for growing temporary crops and which is lying fallow or has not been sown due to unforeseen circumstances. Arable land does not include land under permanent crops or land under protective cover. arboretum: A collection of specimen trees, preferably growing close to a nursery, from which seeds and cuttings can easily be gathered. arboriculture: A general term for the cultivation of trees. archaebacteria: (i). Prokaryotes with cell walls that lack murein, having ether bonds in their membrane phospholipids, that are characterized by growth in extreme environments. (ii). A primary biological kingdom distinct from both eubacteria and eukaryotes. area-time equivalency ratio: It is the ratio of number of hectare-days required in monoculture to the number of hectare-days used in intercropping to produce identical quantities of each of the component crop. argillic horizon: A mineral soil horizon that is characterized by the illuvial accumulation of phyllosilicate clays. The argillic horizon has a certain minimum thickness depending on the thickness of the solum, a minimum quantity of clay in comparison with an overlying eluvial horizon depending on the clay content of the eluvial horizon, and usually has coatings of oriented clay on the surface of pores or peds or bridging sand grains. arid climate: Generally extremely dry climate. W. Koeppen and others have applied the name desert climate for similar conditions of extreme aridity. Annual precipitation usually less than 10 inches. It is not suitable for crop production without irrigation. aridic: A soil moisture regime that has no water available for plants for more than half the cumulative time that the soil temperature at 50 cm below the surface is >5°C, and has no period as long as 90 consecutive days when there is water for plants while the soil temperature at 50 cm is continuously >8°C.

aridisols: Mineral soils that have an aridic moisture regime, an ochric epipedon, and other pedogenic horizons but no oxic horizon. Soil order representing desert ands semi-desert (arid and semi-arid) mineral soils (USA system). Example: Soils of western Rajasthan. Such soils can be (but not always) deficient in sulphur, zinc and iron. Boron toxicity is possible in these soils. aridity index (AI): According to Thornthwaite, the degree of water deficiency below water need at any given station. It is a measure of dryness of a region and is expressed as: AI =

No. of rainy days × Mean precipitation / day Mean temperature + 10

aroma: The distinctive smell imparted by the volatile constituents present in the planting material, its distilled essential oil and oleoresin extract. aromatic compound: Carboxylic compound containing a certain amount of unsaturation in the ring. aromatic: Applied to a group of hydrocarbons and their derivatives characterized by the presence of the benzene ring. arrowing: The flowering in sugarcane is referred as arrowing. arsenic: Arsenic is a highly poisonous semi-metallic element. It can cause bladder, lung, and skin cancer and may cause kidney and liver cancer. Arsenic harms the central and peripheral nervous systems, as well as heart and blood vessels, and causes serious skin problems. It also may cause birth defects and reproductive problems. These health impacts are caused when arsenic contaminates drinking water supplies. It enters water supplies either from natural deposits in the earth or from industrial and agricultural pollution. artesian water: Groundwater confined under hydrostatic pressure. artesian well: A well where the water rises and flows out to the surface because of hydrostatic pressure. artificial water bodies: Areas which are covered by water due to the construction of artifacts such as reservoirs, canals and artificial lakes. Without these structures the area would not be covered by water . arviculture: Crop science. ash: The mineral residue remaining after the destruction of organic material by burning. Ash of plant residues or wood is usually a rich source of potassium.

atomic number assay: Analysis to determine the presence, absence or quantity of a particular chemical or effect. assessing soil quality: Estimating the functional capacity of soil by comparing a soil to a standard such as an ecological site description, a similar soil under native vegetation, a reference soil condition, or quality criteria. The objective of the assessment dictates the standard to be used. associative symbiosis: Phrase referring to a “loose” association between the roots of non-leguminous plants (grasses, wheat, maize, rice, sorghum etc.) and nitrogen-fixing soil bacteria, primarily Azospirillum. asthenosphere: The layer of the Earth’s interior below the lithosphere. The “plastic-like”material in the asthenosphere is weak, able to flow and convect, and the rigid tectonic plates of the lithosphere rest on and move over the asthenosphere. atmometer: An instrument used for measurement of evaporation rate, also called atmidometer or evaporimeter. atmosphere: The atmosphere is the vast gaseous envelope of air that surrounds the Earth. Its boundaries are not easily defined. The atmosphere contains a complex system of gases and suspended particles that behave in many ways like fluids. Many of its constituents are derived from the Earth by way of chemical and biochemical reactions. The Earth’s atmosphere consists of about 79.1% nitrogen (by volume), 20.9% oxygen, 0.036% carbon dioxide and trace amounts of other gases. atmospheric lifetime: The lifetime of a greenhouse gas refers to the approximate amount of time it would take for the anthropogenic increment to an atmospheric pollutant concentration to return to its natural level (assuming emissions cease) as a result of either being converted to another chemical compound or being taken out of the atmosphere via a sink. This time depends on the pollutant’s sources and sinks as well as its reactivity. The lifetime of a pollutant is often considered in conjunction with the mixing of pollutants in the atmosphere; a long lifetime will allow the pollutant to mix throughout the atmosphere. Average lifetimes can vary from about a week (sulphate aerosols) to more than a century (chlorofluorocarbons (CFCs), carbon dioxide). atmospheric nitrogen deposition: Total atmospheric N (NH4+ and NO3–) deposition is of the order of 10-

21

40 kg N ha–1 year–1 in much of northwestern and central Europe and some regions in North America. In less industrial areas, this amount ranges from 3 to 5 kg N ha–1 year–1. Nitrogen deposition is usually not directly included in calculations of N application rates. The amount deposited during the growing season will be considered as N being formed by mineralization of organic matter. Furthermore, this deposition contributes to acidification of agricultural soils, with possible impacts on biodiversity, and to eutrophication of sensitive ecosystems. atmospheric nitrogen: Nitrogen of the air. Air contains 79% nitrogen in gaseous (N2) form, which is referred to as dinitrogen. atmospheric physics: It is the application of physics to the study of the atmosphere. Atmospheric physicists attempt to model Earth’s atmosphere and the atmospheres of the other planets using fluid flow equations, chemical models, radiation balancing, and energy transfer processes in the atmosphere (as well as how these tie in to other systems such as the oceans). atmospheric pressure: The amount of force exerted over a surface area, caused by the weight of air molecules above it. As elevation increases, fewer air molecules are present. Therefore, atmospheric pressure always decreases with increasing height. At sea-level, the average atmospheric pressure is 1013.25 millibars. Pressure is measured by a device called a barometer. atomic absorption spectrophotometer, principles of: Atomic absorption spectrophotometer is based on the principle that when atomic vapours of an element are irradiated by the radiation of a characteristic wavelength (i.e. the light from a source whose emission lines are those of the element in question), they absorb it in direct proportion to the concentration of the element being determined. The unknown concentration is determined by comparison with absorbance measurements of standards of known composition. atomic mass: The mass of a neutral atom expressed in atomic mass units. The atomic mass unit (AMU) is defined as exactly one-twelfth the mass of the carbon isotope. atomic number: The number of positive units of electricity (protons) contained in the nucleus of the atom is equal to the number of negative charges

A

22

A

atomic weight

presented by the electrons, for example, atomic number of hydrogen is 1. atomic weight: The average weight of the neutral atoms of an element existing as a mixture of isotopes in the same ratio as found in nature. auger (soil): A tool for boring holes into the soil. A soil auger is used to withdraw a small soil sample for observation. augmentation cropping: When subcrops are sown to supplement the yield of the main crops, the subcrops are known as augmenting crops, for instance Japanese mustard with berseem, chinese cabbage with mustard. Here the mustard or cabbage helps in getting a higher yield of fodder in spite of the fact that berseem gives a poor yield in the first cutting. auricle: (i). A pair of small ear-like appendages borne at the base of the leaf blade and usually arising at the sides where the ligule and the base of the collar are joined. (ii). An ear-shaped appendage, usually occurring at the junction of the leaf sheath and the blade that may not be present in older leaves. aus rice: A photoperiod-insensitive, rainfed, droughtprone, lowland, or upland rice, broadcast and transplanted during the early part of the wet season from March to September in Bangladesh and from April to August in east India. autecology: (i) The ecology of an individual organism or taxonomic group. (ii). The study of environmental organisms and their effects on plants. autochthonous flora: (i). That portion of the microflora presumed to subsist on the more resistant soil organic matter and little affected by the addition of fresh organic materials. (ii). Microorganisms indigenous to a given ecosystem; the true inhabitants of an ecosystem; referring to the common microbiota of the body of soil microorganisms that tend to remain constant despite constant fluctuations in the quantity of fermentable organic matter. Contrast with zymogenous flora. Also called as oligotrophs. autochthonous: Microorganisms and/or substances indigenous to a given ecosystem; the true inhabitants of an ecosystem; referring to the common microbiota of the body of soil microorganisms that tend to remain constant despite fluctuations in the quantity of fermentable organic matter. autoclave: An airtight chamber that can be filled with steam under pressure or surrounded by another

chamber for the steam and that is used for sterilizing, cooking or other purposes requiring moist temperatures above 212oF or 100°C. Used for sterilization. autotroph: An organism that produces food molecules inorganically by using a light or chemical based sources of external energy. This organism does not require outside sources of organic food energy for survival. autotrophic nitrification: Oxidation of ammonium to nitrate through the combined action of two chemoautotrophic bacteria, one forming nitrite from ammonium and the other oxidizing nitrite to nitrate. autotrophic: Self-nourishing organisms capable of utilizing carbon dioxide or carbonates as the sole source of carbon and obtaining energy for life processes from radiant energy or from the oxidation of inorganic elements or compounds such as iron, sulphur, hydrogen, ammonium and nitrate. Example: green plants, crops, some algae, and nitrifying bacteria. availability (fertilizer): The extent to which the nutrients in a fertilizer can be taken up by crops, often measured approximately (in the absence of a good biological criterion) by solubility in water or dilute acids; also used of soil nutrients to describe the fraction that can be taken up by plants. available nutrient: Form(s) of a plant nutrient in the soil or fertilizer that is immediately or potentially available for being taken up by growing plants during their growth span. This is usually a small fraction of the total nutrient content of the soil. Usually measured in soil testing laboratories for making fertilizer recommendations. Example: sodium bicarbonate-extractable P, CaCl 2-extractable S, DTPA-extractable Zn. In soils, available nutrient status if measured correctly describes the state of soil fertility at that particular time and provides a guideline for external nutrient application. available soil water: The available water capacity of a soil refers to the maximum quantity of water that can be extracted from the soil profile by plants. It is generally defined as the difference in the amounts of water held by a soil when at field capacity and when at its permanent wilting point (-1.5 MPa matric potential). In fact, the soil water content at which non-recoverable wilting occurs is crop dependent. Because of the shape of the water retention curve at low water potentials, precise definition of permanent wilting point is less critical than that of

azotobacter field capacity. If a matric potential of -10 kPa is taken as field capacity, then all soil pores of greater than 30 µm diameter (equivalent cylindrical diameter), are air filled. At wilting point, -1.5 MPa, all pores up to 0.2 µm diameter will be water filled. The available water capacity of a soil will therefore be maximized when its structure is such that the volume of pores of diameter 0.2 µm to 30 µm is maximized. The quantity of available water is expressed usually as either a percent by volume or as mm per given depth of soil. Values range between 6% and 10% (60 mm to 100 mm per 1 m depth of soil) in coarse sands, to about 25% for fine sandy loams (250 mm per 1 m depth of soil). Greater values occur in some highly organic soils and in peats. The available water capacity of clays depends to a great extent on structural development but is usually in the range of 16% to 20%. avalanche: A large mass of snow, ice, soil, or rock, or mixtures of these materials, falling, sliding, or flowing very rapidly under the force of gravity. Velocities may sometimes exceed 500 km/hr. a-value technique: Radio-chemical analysis of plants grown on soils which have been treated with fertilizers containing elements such as radio-active phosphorus; may be used to calculate the phosphorus supply of the original soil. avenue crops: These crop plants are grown along the farm roads and fences such as pigeonpea, sisal, Glyricidia and Tephrosia. average grain/seed weight: This is represented in terms of test weight or seed index in g which shows grain filling behaviour and boldness of grains/seeds of a plant type. When we take the weight of 1000 normally developed bold grains/seeds it is said to be the test weight but weight of 100 such grains is known as seed index. These values are expressed in g/1000 or g/100 for test weight or seed index respectively. avicide: The class of pesticides used to kill birds. axenic culture: A pure culture e.g. culture with organism belonging to a single species. Example: culture of Azotobacter chroococcum or Azospirillum lipoferum. azimuth: The direction, in degrees referenced to true north, that an antenna must be pointed to receive a satellite signal (compass direction). The angular distance is measured in a clockwise direction.

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azolla: Azolla is a fresh water fern found in ponds, ditches, canals and paddy fields. It fixes N in symbiotic association with cynobacterium (BGA) Anabaena Azollae. It is widely used in China and S.R. Vietnam in paddy fields. It requires adequate supply of phosphorus for its growth. It fixes about 25-40 kg N ha-1crop-1. Azolla is an excellent food for fish, ducks and pigs. It is also a good manure and contains 2.08% N, 0.61% P2O5 and 2.05% K2O and has a C:N ratio of 14.0. Azolla can accumulate 30-40 kg K2O ha-1 from irrigation water. Dry Azolla spores @ 5 kg ha-1 or fresh Azolla biomass @ 500 kg ha-1 is the general recommendation for rice fields. Spores should be pre-soaked in water for 12 hours and then inoculated in rice field 7 days after transplanting. Azolla grown with rice crop can be used as a green manure. azomonas: It is a non-symbiotic aerobic nitrogen-fixing bacteria under the family Azotobacteriaceae. Its optimum temperature for growth is 20º-30ºC and pH range is 4.5 to 9.0 (optimum 7.0-7.5). Azomonas has 3 species: Azomonas agilis, Azomonas insignis and Azomonas macrocytogenes. azonal soils: Soils without distinct genetic horizons. (Not used in current U.S. system of soil taxonomy.) azorhizobium: A stem-nodulating bacterium, which is capable of forming root nodules as well as stem nodules on tropical legume Sesbania rostrata. Grouped under Azorhizobium in Rhizobium classification. Example: Azorhizobium caulinodans. azospirillum: These are spiral shaped, microaerophilic, gram negative N-fixing bacteria generally found in association with grass roots. These were originally isolated by Beijerinck in 1925 and named Spirillum lipoferum. They were later siolated by Dobereiner et al. in 1976 in Brazil. The name Azospirillum was given by Terrand. Azospirillum can fix 20-40 kg N ha-1 in association with grass/cereal roots. They also produce hormones like IAA, GA, cytokinins, vitamins and PBH. Three species are reported so far. These are: B. brasilence (isolated from a Brazilian soil), A. lipoferum (fat bearing) and A. pellicle ( develop sub-surface while pellicles). azotobacter: It is a non-symbiotic aerobic free living nitrogen fixing bacteria recommended for cereals, vegetables and flowers. Application is generally done by seed/seedling treatment or soil application. Its foliar application is also reported. Both carrier based

A

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B

back slope

and liquid based Azotobacter fertilizers are available. Azotobacter has ovoid cells of 1.5-2.0 ìm in diameter. It is pleomorphic, gram negative and does not produce endospores. It forms cysts which is the dormant stage in life cycle giving rise to vegetative cells. Once inoculated its population is about 102103/g soil. Application of organic matter along with Azotobacter helps in N-fixation; fixes 10-20 mg N/g of carbohydrate with the help of nitrogenase enzyme. After the cells die, the fixed-N is released in the soil. In addition to nitrogen, Azotobacter also synthesizes some growth promoting substances. These are gibberlins and cytokinins, nicotinic and pantothenic acids, biotin and heteroauxins and PBH (Poly beta hydroxybutyric acid). Azotobacter is also reported to produce fungistatic substances that suppress plant pathogens and control plant pathogens. Six species of Azotobacter are reported. These are A. armeniacus (isolated in Armenia), A. beijerinckii (named after Beijerinck), A. chroococcum (due to coloured coccus), A. nigricans (black in colour), A. paspali (isolated from the grass Paspalum rotatum) and A. vinelandi (isolated from Vineland, New Jersey, USA).

B back slope: The geomorphic component that forms the steepest inclined surface and principal element of many hillsides. Back slopes in profile are commonly steep, are linear, and may or may not include cliff segments. backfurrow: The resulting ridge of soil turned up when the first furrow slice is lapped over the previous soil surface when starting the ploughing operation. backswamp: A marshy, depressed area on the flood plain between a natural levee or a flood-plain step and the adjacent terrace, till plain, or valley side. bacterial count: Number and kind of bacteria per unit volume or weight of a substance, such as soil. Bacterial population represents group of bacteria present in the environment and is expressed as 104/g soil etc. bacteriocin: A specific toxin produced by bacteria. Example: Cicer (chickpea) rhizobia PR-15 and PR42 produce bacteriocin, which plays an important role in inter-strain competitiveness for nodulation. bacteriorrhiza: Refers to symbiosis between a plant root (rhizo = root) and bacteria, as in the case of a legume and rhizobia.

bacterisation: It is the process of coating the seeds with bacterial culture such as of Rhizobium, Azotobacter etc. bacterium (Gr. Bakterion, a stick; pl: bacteria): Common name for the class Schizomycetes: minute (0.5-5 µm), unicellular organisms, without a distinct nucleus. Bacteria are prokaryotes and most of them are identified by means of Gram staining. They are classified on the basis of their oxygen requirement (aerobic vs. anaerobic) and shape (spherical = coccus, rod like = bacillus, spiral = spirillum, comma-shaped = vibrio, corkscrew-shaped = spirochaete and filamentous). Bacteria usually reproduce asexually, by simple cell division, although a few undergo a form of sexual reproduction, termed conjugation. A few bacteria can photosynthesize (including greenblue cyanobacteria), some are saprophytes and others are parasites, which can cause diseases. bacteroids: An altered form of bacterial cells. Refers particularly to the swollen, irregular vacuolated cells of Rhizobium and Bradyrhizobium in legume nodules. badlands: A land type nearly devoid of vegetation, especially a region where erosion has cut the land into an intricate maze of narrow ravines, sharp crests and pinnacles, resulting from serious and semi-arid erosion of soft geologic materials. Most common in arid regions. bagasse: The mill residues from the cane sugar industry consisting of crushed stalks from which the juice has been extracted. It is inevitable that any other form of fuel required for evaporating water from the sugarcane juice would be costlier than bagasse, which is available free of cost and at the point where it is needed. Some of it is currently used for making cardboard but good quality paper can also be manufactured from it. As a bulky manure it is low in plant nutrients. On an average it contains 0.6% N, 0.3% P2O5 and 25% organic carbon, giving it a C:N ratio of about 42:1. Therefore just like wheat or rice straw for better use it has to be first composted. Alternatively cellulolytic organisms such as Aspergillus awamorii have to be used for its fast decomposition. Bagasse can also be used for producing biogas and the spent-slurry is richer and may contain 1.5-1.8% N, 1-1.3% P2O5 and 0.6-0.8% K2O on dry weight basis. Bagasse makes up about one-third of cane and thus in the year 2003-04 about 79 million tonnes (M t) of bagasse was produced in the country (taking the sugarcane production value

bandwidth

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of 237 M t). However, since bagasse is produced at sugar/jaggery units its use as a manure has to be restricted to the vicinity of those units.

the high-altitude tropics that have only a sparse ground cover of herbs, grasses, mosses and ferns. Sometimes also found in the lowlands.

balanced crop nutrition: Represents that status of crop nutrition when all essential plant nutrients are present at optimum levels and ratios so that there are neither any deficiencies nor excesses. The goal of scientific nutrient recommendations is to provide balanced crop nutrition. Plants need a proper supply of all macronutrients and micronutrients in a balanced ratio throughout their growth. Liebig’s law of the minimum governs the basics of balanced fertilization. Formerly, it was rightly concluded that, on many soils, the application of N without simultaneous supplies of phosphate and K made little sense. Today, in view of multiple nutrient deficiencies and increasing costs of crop production, fertilization with N or NPK without ensuring adequate supplies of all other limiting nutrients (S, Zn, B, etc.) makes little sense and, in fact, becomes counterproductive by reducing the efficiency of the nutrients that are applied. Balanced crop nutrition is not the same as balanced fertilization. The latter should make the former possible. For example, only soils equally poor in available N, P and K should be fertilized with these three nutrients in balanced amounts. This can best be done using soil-test and crop removal data. Where a soil is rich in one nutrient, fertilization should be directed to the deficient nutrients in order to make balanced crop nutrition possible. Thus, the goal is not balanced fertilization as such but balanced crop nutrition through balanced nutrient application in order to supplement those nutrients that are deficient in the soil.

band placement: Refers to fertilizer application by hand or by machine, in bands or strips on or under the soil surface. Usually done below and to the side of the seed row during planting. Results in limited soil-fertilizer contact, since the entire field is not uniformly treated as during a surface broadcast application. This can be done either by hand or by special planting and/or fertilizer drilling equipment (seed-cum-fertilizer drill). It is preferably used for row crops, which have relatively large spaces between rows (maize, cotton, and sugar cane); or on soils with a tendency to phosphate and potassium fixation; or where relatively small amounts of fertilizer are used on soils with a low fertility level. Where crops are cultivated by hand and planted in hills, the recommended number of grams of fertilizer are placed in the row or planting hole (preferably measured out in an appropriate tin or pot), under, or beside the seed, and covered with soil. Great care has to be taken that no fertilizer is placed either too close to the seed or to the germinating plant to avoid toxicity, i.e. salt damage to the seedling (burning of the roots).

balanced fertilizer use (BFU): The application of nutrients in proportions best suited to the needs of the crop taking account of the amounts of each supplied by the soil. Classically equated with NPK application but in view of widespread multiple nutrient deficiencies, BFU includes apart from NPK application, required secondary and micronutrients. It is a pre-requisite for efficient fertilizer use. ballast elements: Elements such as aluminium and silicon have been called ballast elements because they are generally present in large amounts, although the plant can grow normally without them. bamboo: A vegetation type consisting of woody graminaceous species from the subfamily Bambusoideae. Found as dense thickets or forest in

band: In radio, a continuous sequence of broadcasting frequencies within given limits. In radiometry, a relatively narrow region of the electromagnetic spectrum to which a remote sensor responds; a multispectral sensor makes measurements in a number of spectral bands. In spectroscopy, spectral regions where atmospheric gases absorb (and emit) radiation. banding: It is a method of fertilizer or other agrochemical application above, below, or alongside the planted seed row. Refers to either placement of fertilizers close to the seed at planting or subsurface applications of solids or fluids in strips before or after planting. Also referred to as band application. bandwidth: The total range of frequency required to pass a specific modulated signal without distortion or loss of data. The ideal bandwidth allows the signal to pass under conditions of maximum AM or FM adjustment. (Too narrow a bandwidth will result in loss of data during modulation peaks. Too wide a bandwidth will pass excessive noise along with the signal.) In FM, radio frequency signal bandwidth is determined by the frequency deviation of the signal.

B

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B

bao

bao: A floating rice mixed crop of aus and aman rice, i.e., early and late varieties sown during the early part of the wet season. A practice frequently used in Assam, India. bar: (i). A generic term for ridge-like accumulations of sand, gravel, or other unconsolidated material formed in the channel, along the banks, or at the mouth of a streams or formed by waves or currents as offshore features in large lakes or oceans. (ii). A unit of pressure equal to one million dynes per square centimetre. Megapasal is, however, the preferred unit for pressure. bare rock: This includes areas where rock is surfacing over more than 60 percent of the area. barograph: A self-recording barometer in which continuous trace of the atmospheric pressure is made on a barogram. barometer: Instrument that measures atmospheric pressure. standard mercury barometer has a glass column about 30 inches long, closed at one end, with a mercury-filled reservoir. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir. High atmospheric pressure forces the mercury higher in the column. Low pressure allows the mercury to drop to a lower level in the column. An aneroid barometer uses a small, flexible metal box called an aneroid cell. The box is tightly sealed after some of the air is removed, so that small changes in external air pressure cause the cell to expand or contract. barrage: (i). Any artificial obstruction placed in water to increase water level or divert it. Usually the idea is to control peak flow for later release. (ii). A large structure erected across a river in order to store water, usually for irrigation. basal dressing: Fertilizer or manure applied before or at planting time. Same as pre-plant application. Most secondary and micronutrients meant for soil application are part of the basal dressing along with part of N and the full rate of P and K for annual crops. base (period): Period in days during which irrigation is supplied to a crop. base crop: Base crop or main crop is one which is planted at its optimum sole crop population in an intercropping situation and the second crop is planted in between rows of the main or base crop.

base exchange: The physio-chemical process in soils involving the exchange of one basic cation (Ca2+) with another (Mg2+ or K+). Common phenomenon in soils, having profound effect on nutrient retention and release into the soil solution and thus nutrient availability to the plant roots. base saturation: It is closely related to cation exchange capacity is the base saturation, which is the fraction of exchangeable cations that are base cations (Ca, Mg, K and Na). It can also be defined as the amount of basic cations that occupy the cation exchange sites, divided by the total cation exchange capacity (CEC). The value of the base saturation varies according to whether the cation exchange capacity includes only the salt extractable acidity (see cation exchange capacity) or the total acidity determined at pH 7 or 8. Often expressed as a percent. Base Saturation % = (Exchangeable bases ÷ CEC) × 100 The higher the amount of exchangeable base cations, the more acidity can be neutralised in the short time perspective. Thus, a site with high cation exchange capacity takes longer time to acidify (as well as to recover from an acidified status) than a site with a low cation exchange capacity (assuming similar base saturations). base temperature: The temperature from which the rate of development of a plant organ increases more or less linearly as temperature increases up to an optimum temperature, above which the rate of development decreases. Base temperatures need to be determined by experiment. baseline data: Fundamental units of basic inventory information that is crucial for biodiversity conservation, planning and management. These are both biotic and abiotic and usually include: (i) the presence and/or abundance of species and other units; (ii) other dependent biotic data (e.g. plant cover for macroarthropods); (iii) the appropriate influential abiotic variables, and (iv) human variables. basic fertilizer: One that, after application to and reaction with soil, decreases residual acidity and increases soil pH. basic intake rate: Rate at which water will enter the soil when after initial wetting of the soil the rate becomes essentially constant; which is equal to saturated hydraulic conductivity; the unit being mm/hr. basic research: Research that deals with fundamental principles of organisms.

benchmark soil basic slag: It is a by-product of steel industry. Generally a double silicate and phosphate of lime [(CaO)5P2O5SiO 2]. Can contain 10-18% P2O5 (part of which is citrate soluble), 35% CaO, 2-10% MgO and 10% Fe. Basic slag can be used as a fertilizercum-soil conditioner because it contains lime and citric acid soluble P. The steel slags are very hard and cannot be used as such. Their use in agriculture is possible only if they are ground to a fine state. Fineness is necessary to have a close contact of the slag particles with soil particles for better dissolution and availability of nutrients from it. basic vegetative phase (BVP): The juvenile growth stage of a plant that is not affected by photoperiod. basin irrigation: An irrigation method in which crops are surrounded by a border to form a submersion check called basin of round, square or any other form. Irrigation water generally comes directly from the supply ditch/canal or from other basins. This method is suitable for fruit crops. Basins are generally round in shape, occasionally square in shape. The basins are small when the trees are young and their size is increased with age of the trees. Basins are connected by an irrigation channel. basin: In the context of hydrology and related subjects this includes a drainage area of a stream, river or lake. basophiles: Plants, which can grow well in alkali soil (pH 7.4 - 8.5). batch culture/fermentation: It is a culture in which microorganisms are grown on a limited amount of medium until either one essential nutrient is exhausted or toxic by-products accumulate to growth-inhibiting levels. It passes through different stages (lag phase, log phase, stationery phase and decay phase). During batch fermentation, the fermentation is allowed to continue for 4 to 10 days, passing different stages. After completion of fermentation, the cells are removed from the broth medium. baule unit: It is a classical term for the amount of a plant nutrient, which is associated with 50% of the maximum yield. If 50% of maximum yield is obtained with 1 Baule unit of a nutrient (say 5 kg S/ha), then 75% yield is associated with 2 Baule units, 87.5% of maximum yield with 3 Baule units and so on. Also used to describe the nutrient supplying power or fertility of a soil in terms of its ability to support crop yield.

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bed load (erosion): The sediment that moves by sliding, rolling, or salting on or very near the streambed; sediment moved mainly by tractive or gravitational forces or both but at velocities less than the surrounding flow. bed planting: A method of planting in which the seed is planted on slightly raised areas between furrows with two or more seed rows sometimes planted on each bed. bed: Narrow flat-topped ridge on which crops are grown with a furrow on each side to facilitate irrigation and for drainage of excess water; or an area in which seedling or sprouts are grown before transplanting. bedding (soil): Preparing a series of flat-topped parallel ridges usually no wider than two crop rows, separated by shallow trenches usually less than the width between crop rows. bedding: Material such as straw, sawdust, wood shavings, shredded newspaper, sand or other similar material used in animal confinement areas for the comfort of the animal or to absorb excess moisture. Bedding can drastically affect the characteristics of the manure, and must be taken into consideration in the design of the storage facility. bedrock: A general term for the solid rock that underlies the soil and other unconsolidated material or that is exposed at the surface. Beer’s law: In absorption spectroscopy, the absorbance of a dilute solution is equal to its absorptivity times the path length times the concentration of the absorbing solute. beijerinckia: An aerobic nitrogen-fixing bacteria. It closely resembles Azotobacter indicum and grows well under acid conditions. It has four species, e.g. Beijerinckia derxii, Beijerinckia fluminensis, Beijerinckia indica (earlier known as Azotobacter indicum) which is highly acid tolerant and Beijerinckia mobilis. benchmark soil: A benchmark soil is one of large extent, holds a key position in the soil classification system, or is of special significance to farming, engineering, forestry, livestock production, or other uses. The purpose of benchmark soils is to focus data collection and research efforts on soils that have the greatest potential for expansion of data and interpretations.

B

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benchmark

benchmark: A point of reference for measurements as in topographical surveys and land leveling.

B

benefit cost ratio (BCR): It is the ratio of the value of extra crop produced (minus cost of fertilizer or any other production input) to the cost of fertilizer. Indicates the rate of net returns from the use of an input and hence is an important indicator of the degree of profitability from input use. If a fertilizer costing Rs. 500 produces extra crop worth Rs1500, then the BCR = 2 (1500 - 500 divided by 500). A useful decision making tool before investing in an input. benthos: Organisms living on or in the bottom of oceans, seas, rivers, lakes and other water bodies. Depending on the size of the organisms, benthos are regarded as macrobenthos (organisms > 1000 µm), meiobenthos (organisms between 42 µm and 1000 µm) and nanobenthos or microbenthos (organisms < 42 µm). Depending on the depth distribution, benthos are regarded as epibenthos (living between low water line and 200 m depth), mesobenthos (living at depths between 200 and 1000 m), hypobenthos (living between 1000 and 2000 m) and abyssal benthos (living below 2000 m). bentonite: A relatively soft rock formed by chemical alteration of glassy, high silica content volcanic ash. This material shows extensive swelling in water and has a high specific surface area. The principal mineral constituent is clay size smectite. berms: (i). An elongated mound in a naturally level land area or one made artificially by a landscaper to gain privacy or interest in a private or public area. (ii). A shelf or mound that breaks the continuity of a slope. best management practices (BMPs): A practice or combination of practices to be effective and practicable (given technological, economic and institutional considerations) to manage nutrients to protect surface water and groundwater. Those practices include, but are not limited to: conservation tillage, crop rotation, soil testing, manure testing, stormwater management practices and nutrient application. beushaning / bushening: It refers to cross ploughing of field in 4-5 cm standing water after about 30 days of crop emergence. It reduces early crop-weed competition, soil permeability and thus leads to better utilization of nutrients particularly nitrogen and water. Bushening is prevalent in parts of Madhya Pradesh

and Orissa and is generally followed by khelua i.e. gap filling with seedlings from the same field after about a week. beverages: Products of crops used for mild, agreeable and stimulating liquors meant for drinking such as tea, coffee, cocoa. biennial crops: Crop plants having a life span of two consecutive years. The first year’s growth is purely vegetative with top growth usually confined to rosette of leaves. The taproot is often fleshy and serves as a food storage organ. During the second year it produces a flower stalk from the crown. After producing seed the plant dies, for instance sugarbeet, beet, cabbage, radish, carrot. Due to unfavourable weather conditions, a floral stalk may come out (bolting) even in the first year. biennial: Plant species that complete their life-cycles from seed germination to fruiting in two years. bioaccumulantion: The increase in concentration of a substance in living organisms, as they take in contaminated air, water, or food, due to slow metabolization and excretion. bioassay: A biological analysis performed on living cells or on a living organism, sometimes to detect minute amount of a substance which influences growth. Quantitative estimation of biologically active substances. bioaugmentation: Bioaugmentation is the practice of adding specialized microbes or their enzyme preparations to polluted matrices to accelerate transformation or stabilization of specific pollutants. bioavailable: Substance available to living organisms (bacteria, plants). biochemical oxygen demand (BOD): A measure of the amount of oxygen consumed by natural, biological processes that break down organic matter, such as those that take place when manure or sawdust is put in water. High levels of oxygen-demanding wastes in waters deplete dissolved oxygen (DO) thereby endangering aquatic life. Sometimes referred to as biological oxygen demand. BOD is a standard measure of water quality. Chemical oxygen demand (COD) is a measure of the oxygen consumed when organic or inorganic matter is oxidized in water chemically, rather than biologically. bioconversion: It is the conversion of organic materials, such as plant or animal waste, into usable products

biofuel or energy sources by biological processes or agents, such as certain microorganisms or enzymes. New cellulosic ethanol conversion processes have enabled the variety and volume of feedstock that can be bioconverted to expand rapidly. Feedstock now includes materials derived from plant or animal waste such as paper, auto-fluff, tires, fabric, construction materials, municipal solid waste (MSW), sludge, sewage, etc. biodegradable: A substance, which can be broken down or decomposed as a result of biochemical changes normally involving bacteria or fungi e.g. cellulose is degradable by cellulose decomposing fungi. This property is utilized for reducing the composting time by inoculating the material to be composted with suitable microbes. biodiesel: An alternative renewable fuel, produced from vegetable oils or animal fats through a refinery process called transesterification. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. Biodiesel is most commonly used as a blend of 20% biodiesel and 80% conventional diesel (called “B20”). Its use can result in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter. biodiversity: The term biodiversity was coined in 1985, (abbreviating ‘biological diversity’) and has been defined in many different ways. In general, it is the variety and variation among plants, animals, and microorganisms, and among their ecosystems. It has 3 levels: ecosystem diversity, species diversity, and genetic (within species) diversity. Genetic diversity provides resources for genetic resistance to pests and diseases. In agriculture, biodiversity is a production system characterized by the presence of multiple plant and/or animal species, as contrasted with the genetic specialization of monoculture. Advocates of maintaining biodiversity hold that civilization should preserve the greatest possible number of existing species so that a highly diverse genetic pool, which might be tapped for useful and beneficial characteristics, will be available into the future; and argue further that damage to the planet’s biodiversity risks harm with effects on humans that can not be predicted with current knowledge. bio-drainage: Bio-drainage uses the evapotraspirative power of vegetation, especially trees to keep groundwater tables deep.

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biodynamic agriculture/ farming: Biodynamic farming is an approach based on the work of Austrian philosopher Rudolf Steiner. Biodynamic agriculture’s aim is to grow the highest quality food possible while at the same time working to heal the earth. No synthetic pesticides, herbicides, or fertilizers are used. Biodynamic agriculture recognizes that food is not merely a chemical composition of matter but also needs to contain forces gathered from the sun, moon, and stars which nourish not just our physical bodies but also our emotional and spiritual selves. bioenergy (=biomass energy): Energy made available by the combustion of materials derived from biological sources. A renewable energy source that makes use of such biofuels as methane (biogas) generated by sewage, farm, industrial, or household organic waste materials. Other biofuels include trees grown in so-called “energy forests” or other plants, such as sugar cane, grown for their energy potential. biofertilizer: Biofertilizers are products containing living or dormant microorganisms like bacteria, fungi, actinomycetes, algae alone or in combination, which an application help in fixing atmospheric nitrogen or solubilize/mobilise nutrients in addition to secretion of growth promoting substances for enhancing crop growth. The word ‘biofertilzier’ is made by adding the prefix ‘bio’ (living) before the world fertilizer (materials supplying essential plant nutrients). Strictly speaking the word ‘biofertilizer’ is a misnomer, because biofertilizers do not supply plant nutrients per se except Azolla when used as green manure. Biofertilizers are broadly classified into 4 categories, namely nitrogen fixers, phosphate solubilizers (PSB or PSM), compost accelerators and plant growth promoting Rhizobacteria. In addition VAM (vesicular arbuscular mycorrhiza) are also used for enhancing the availability of native soil P. biofuel: (i); Gas or liquid fuel made from plant material (biomass). Includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulfite liquors, agricultural waste, straw, tires, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline. (ii); It is derived from biomass — recently living organisms or their metabolic byproducts, such as manure from cows. It is a renewable energy source, unlike other natural resources such as petroleum, coal, and nuclear fuels. Like coal and petroleum, biomass is a form of stored solar energy. The energy

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biogas (gobar gas) plant

of the sun is captured through the process of photosynthesis in growing plants. Agricultural products specifically grown for use as biofuels include corn and soybeans, primarily in the United States; flaxseed and rapeseed, primarily in Europe; sugar cane in Brazil; palm oil in South-East Asia; and jatropha (though not an agricultural product) in India. Biodegradable outputs from industry, agriculture, forestry and households can be used; examples include straw, timber, manure, rice husks, sewage, biodegradable waste, and food leftovers. They are converted to biogas through anaerobic digestion. biogas (gobar gas) plant: Since more than 50 per cent of cow dung available in the country is made into cow dung cakes and burnt as cooking fuel, installation of a biogas plant is suggested as an alternative. This produces methane which can be used for cooking in the kitchen, for lightening the home and even for running tubewell pump. Also the biogas slurry is richer in plant nutrients. In India the first attempt was made by S.V. Desai of Indian Agricultural Research Institute, New Delhi in the early 1940s. Later, in the year 1946, V.M. Joshi, working near Bombay, designed a plant which produced 20 to 40 cubic feet gas per day. During the year 1950, Jashbhai J. Patel introduced some more innovations in biogas units. The renowned Gandhian economist, J.C. Kumarappa has also advocated the biogas units permitting cow dung for manure as well as for cooking gas. Shri Ram Bux Singh of Gobar Gas Research Station, Ajitmal, Etawah, has made certain experiments to make use of methane gas as an alternative source of future energy. His attempts in running an oil engine as well as generators which drive a 10 h.p. electric motor have been successful. In addition, Mr. Singh has developed room-heaters and spinning wheels which can run on methane gas. With the help of this heat, he was also able to mould plastic wares. The major components of a gobar gas plant are: (i) a digester where the anaerobic fermentation takes place; (ii) gas holder for collecting the biogas; (iii) input and output units for feeding the effluent and storing it; and (iv) gas distributing system. Several types and models of biogas plants exist. These are based on the arrangement of the gas holder in the plant and the mode of flow of the slurry through the plant. biogas production: Methodology and steps in the production of biogas. The three step process involves (i) hydrolysis of complex materials (ii) acid

production, and (iii) methane fermentation. The first step is enzymatic. In the second step acid forming bacteria convert soluble organic compounds into acids of which acetic acid is the main one and the third step is carried out by methanogenic bacteria. biogas slurry: It is a semi-solid residual end product of a biogas plant. Its typical composition is 1.41.8% N, 1.1-1.7% P2O5 and 0.8-1.3% K2O and is useful organic manure. There are several advantages of biogas slurry: (i). Biogas slurry is quite rich in nitrogen than the original ingredients due to addition of living and dead micro-organisms., (ii). Biogas slurry also contains phosphates, potash, sulphur and a number of micro-nutrients like zinc and iron. (iii). Biogas slurry is extremely cheap and is made by locally available material. (iv). The prolonged use of organic manure maintains as well as builds the soil fertility. It has been reported that the biogas spent slurry is far better than FYM, since it is well digested and has higher nutrient content. biogas: Gas generated by the anaerobic fermentation of organic matter (dung, plant residues, and so on). Biogas is comprised primarily of methane and carbon dioxide. It contains about 60 - 70% methane. Desai and Biswas in India first demonstrated production of combustible gas from cow dung by anaerobic fermentation in 1975. As a renewable energy source, it can be used for heating, lighting and, with suitable adaptation, as fuel for internal combustion engines. biogeochemical cycling: Cycling of chemicals through the biosphere, lithosphere, hydrosphere, and atmosphere. biogeochemistry: It involves scientific study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the hydrosphere, the pedosphere, the atmosphere, and the lithosphere), and the cycles of matter and energy that transport the Earth’s chemical components in time and space. Biogeochemistry is a systems science. bioinoculant: A biological preparation containing living organisms such as biofertilizers, used in agriculture for inoculation of seeds, soils or other plant materials. biological (=biotic) resources: Includes genetic resources, organisms or parts thereof, populations, or any other biotic component of ecosystems with direct, indirect or potential use or value for humanity.

biological soil crust biological amplification (=biomagnification): Increase in concentration of toxic fat-soluble chemicals in organisms at successively higher trophic levels of a grazing food chain or food web because of the consumption of organisms at lower trophic levels. For example, chlorinated pesticides concentrate in the fat and skin of fish in contaminated lakes and streams and are biomagnified when those fish are eaten by larger fish, and perhaps eventually by mammals or birds of prey. biological availability: That portion of a chemical compound or element that can be taken up readily by living organisms. biological control of weeds: It involves utilization of natural living organisms (bioagents) such as insects, pathogens and competitive plants to limit the weed infestation. The objectives of biological control are not eradication, but reduction and regulation of the weed population below the level of economic injury. A bioagent may be either specific or non-specific. Specific bioagent attacks only one or two specific weeds, while the non-specific feed upon a variety of vegetation. biological control: The practice of using beneficial natural organisms to attack and control harmful plant and animal pests and weeds is called biological control, or biocontrol. This can include introducing predators, parasites, and disease organisms, or releasing sterilized individuals. Biocontrol methods may be an alternative or complement to chemical pest control methods. biological denitrification: Loss of nitrogen from the soil due to microbial activity. Microbial reduction of oxidized inorganic nitrogen compounds serving as nominal electron acceptors in anaerobic respiratory pathways lead to nitrogen losses to the atmosphere as N2 or N2O. biological determinants of cropping systems: The biological factors such as crop species, varieties, weeds, insect-pests, and diseases, which determine the crop configuration and performance of a cropping pattern at a given site. biological herbicide(=bio-herbicide): A naturally occurring substance or organism which kills or controls undesirable vegetation/weeds. Preferred over synthetic chemicals because of reduced toxic effect on the environment.

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biological interchange: The interchange of elements between organic and inorganic states in a soil or other substrate through the action of living organisms. It results from the biological decomposition of organic compounds with the liberation of inorganic materials (mineralization) and the utilization of inorganic materials with synthesis of microbial tissue (immobilization). biological nitrogen fixation (BNF): It is conversion of nitrogen (N2) gas into ammonia through a biological process. Many microorganisms are able to convert nitrogen in the air to ammonia for use as their nitrogen source. Rhizobium species living in symbiotic relationship in root nodules of legumes (e.g. soybean, clover, alfalfa, peas, beans) can convert atmospheric N2 gas to NH3, which is further converted to amino acids and proteins. In exchange, the legumes provide the Rhizobium species with the energy they need to grow and to fix N2. Some non-leguminous trees and plants (e.g. alder, sugarcane) also host N-fixing bacteria. Photosynthetic cyanobacteria are also Nfixing organisms and are especially important in rice paddies. The amount of N fixed varies greatly from crop to crop, ranging from a few kg to a several hundred kg N ha-1 year-1. The process is depressed when other sources of N are abundant, and is also reduced in acid soils and in soils with low P availability. biological oxygen demand (BOD): The amount of oxygen required to stabilize the demands from aerobic action in the decomposition of organic matter. biological soil crust: It is also called microbiotic, microphytic, cryptobiotic or cryptogamic crusts. A living community of bacteria, microfungi, cyanobacteria, green algae, mosses, liverworts, and lichens that grow on or just below the soil surface. Biological crusts can heavily influence the morphology of the soil surface, stabilize soil, fix carbon and nitrogen, and can either increase or decrease infiltration. The percent cover and the components of the crust can vary across short distances. Identification of biological crust organisms is simplified through the use of three broad morphological groups: The cyanobacteria group includes cyanobacteria and green algae. The moss group includes short and tall mosses, but not club moss mats, such as those in northern latitudes, or spike moss. The lichen group includes crustose, gelatinous, squamulose, foliose, and fruiticose lichen, as well as liverworts.

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biological systems

biological systems: Refers to cropping and livestock systems.

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biological yield: In agriculture, total production of plant material per unit area in a given time. Example: tonnes of grain + straw per hectare. Same as dry matter or biomass but not same as grain yield. biologics: Immunization materials made from living or “killed” organisms and their products used for the detection and prevention of diseases; includes serums, vaccines, bacterins, antigens, and antitoxins. biomass: In the broad sense the total weight of living or recently living matter, derived from animals and plants. Often referring to plant biomass which includes all the components of plants - stems, leaves, bark, flowers, etc. Usually expressed as dry weight per unit area. Biomass should not be confused with productivity, the actual rate at which organic matter is created. biome: Ecological regions as a result of complex interactions of climate, geology, soil type, water resources and latitude. These components together determine what types of plant and animal life exist in different places. UNESCO has designated fourteen major biomes. biomethanation: This is a process of production of methane and associated gases through anaerobic digestion of organic residues including the wastes obtained through various sources. biomineralization: It is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. Examples include silicates in algae, carbonates in diatoms and invertebrates, and calcium phosphates and carbonates in vertebrates. These minerals often form structural features such as sea shells and the bone in mammals and birds. Other examples include copper, iron and gold deposits involving bacteria. As a result biomineralization is employed in metal extraction. The aim of biomimetics is to mimic the natural way of producing minerals such as apatites. Many manmade crystals require elevated temperatures and strong chemical solutions whereas the organisms have long been able to lay down elaborate mineral structures at ambient temperatures. Biominerals generally consist of either calcium, iron, or silicon. The hardness of biominerals depends on both the degree of mineralisation (i.e., structure) and the type of mineral.

biomining: It is a new approach to the extraction of desired minerals from ores being explored by the mining industry in the past few years. Microorganisms are used to leach out the minerals, rather than the traditional methods of extreme heat or toxic chemicals, which have a deleterious effect on the environment. Using a bacterium such as Thiobacillus ferooxidans to leach copper from mine tailings has improved recovery rates and reduced operating costs. Moreover, it permits extraction from low grade ores - an important consideration in the face of the depletion of high grade ores. biopesticide (=biological pesticide): (i). A generic term, not specifically definable, but generally applied to a biological control agent, usually a pathogen, formulated and applied in a manner similar to a chemical pesticide, and normally used for the rapid reduction of a pest population for short-term pest control. (ii). A pesticide that is biological in origin (i.e., viruses, bacteria, pheromones, natural plant compounds) in contrast to synthetic chemicals. Transgenic Bt cotton and corn are biopesticides because Bacillus thuringiensis (Bt) is a naturally occurring soil bacterium that has been genetically engineered into the plants. biopharmaceutical (biopharm) crops: Crops that are bioengineered to produce pharmaceuticals, industrial chemicals and other medical and industrial products (sometimes called plant-made pharmaceuticals). Controversy surrounds the effect that these crops might have on native plants if cross pollination takes place. The flow of genetic modifications from bioengineered crops to their conventional native counterparts is a matter of concern to scientists and regulators. biopiracy: Bioprospecting regarded as the perpetuation of the colonial habit of plundering other countries’ biological resources without fair and equitable compensation, resulting in environmental, economic and social detriment. bioregion: A unique region on the Earth that has distinct soils, landforms, watersheds, climates, native plants, and animals, and/or other particular natural characteristics. bioremediation: (i). Bioremediation describes several technologies and practices that take advantage of natural systems and processes to clean up pollution. The technologies entail the science of understanding

biuret natural processes that promote and accelerate destruction, transformation, removal, or stabilization of pollutants. Practices involve implementation and management of strategies that enhance those processes. (ii). The use of biological agents to reclaim soils and waters polluted by substances hazardous to human health and/or the environment; it is an extension of biological treatment processes that have been used traditionally to treat wastes in which micro-organisms typically are used to biodegrade environmental pollutants. biosafety: Safety aspects related to the application of biotechnologies and to the release into the environment of transgenic plants and other organisms particularly microorganisms that could negatively affect plant genetic resources, plant, animal or human health, or the environment. biosalinity: It is the study and practice of using saline (salty) water for irrigating agricultural crops. Many arid and semi-arid areas actually do have sources of water, but the available water is usually brackish (5005000 ppm salt by weight) or saline (3-5% salt). The water may be present in underground aquifers or as seawater along coastal deserts. With traditional farming practices, saline water results in soil salinization, rendering it unfit for raising most crop plants. biosecurity: Biosecurity refers to agricultural practices intended to reduce or prevent the introduction of infectious diseases on a farm or other production facility, and includes practices such as limiting access by personnel and vehicles, reviewing and screening introduced items such a seed, feed and new animals, and controlling vermin. More recently, biosecurity programs have incorporated elements to protect against terrorism, vandalism, and other intentional acts that could compromise disease control, whether or not they were the primary aim of the illicit acts. biosequence: A group of related soils that differ, one from the other, primarily because of differences in kinds and numbers of plants and soil organisms as a soil-forming factor. biosolids composting: The process involving the aerobic biological degradation or bacterial conversion of dewatered biosolids that works to produce compost,which can be used as a soil amendment or conditioner. biosolids: (i). The solid, slime-solid, or liquid residue generated during the treatment of (domestic) sewage

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in a wastewater treatment facility. The definition also includes a material derived from biosolids (i.e. biosolids to compost). (ii). The processed solids that have been separated from the liquid portion of municipal wastewater during treatment. biosphere reserve: Established under UNESCO’s Man and the Biosphere (MAB) Programme, biosphere reserves are a series of protected areas linked through a global network, intended to demonstrate the relationship between conservation and development. biosphere: The portion of earth and its atmosphere that can support life. Generally the transition zone between earth and atmosphere, where most forms of terrestrial life are commonly found. biostimulation: As the name implies, this strategy involves some stimulation of the numbers and activities of natural populations, usually bacteria or fungi, so they can better break down pollutants into harmless products. Biostimulation is based on the assumption that a polluted medium (soil, water, etc.) already contains microbes that are capable of destroying or detoxifying particular pollutants in that medium. biosuper: A fortified fertilizer containing elemental sulphur and rock phosphate, which has been inoculated with S-oxidizing bacteria to convert elemental S to sulphuric acid. The acid in turn solubilises rock-P to make its P plant-available. Used mainly in Australia and New Zealand. biotic factor: The influence upon the environment of organisms owing to the presence and activities of other organisms, as distinct from a physical, abiotic, environmental factor. biotic: Live and living organisms. biotite: A brown, trioctahedral layer silicate of the mica group with Fe(II) and Mg in the octahedral layer and Si and Al in a ratio of 3:1 in the tetrahedral layer. birefringence: The numerical difference between the highest and lowest refractive index of a mineral. Minerals with birefringence exhibit interference colours in thin section when viewed with crossedpolarized light. biuret: Refers to the product formed at high temperature during the manufacture of urea. Formula: H2NCONHCONH2. It is toxic to plants. Biuret

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black (cotton) soil

content is an important criteria when urea is applied through foliar application. In view of this, in most standard specifications for urea, a maximum biuret limit of 1-1.5% is prescribed. black (cotton) soil: Soil of black colour (throughout the profile) with low organic matter and a high clay content, exhibiting a strong phenomenon of swelling and shrinkage; during dry periods cracks develop that may be several cm wide and more than 50 cm deep. These vary in depth from shallow to deep. The typical soil derived from the deccan trap is the regur or black cotton soil. It is common in Maharashtra, western parts of Madhya Pradesh, parts of Andhra Pradesh, parts of Gujarat and some parts of Tamil Nadu. It is comparable with the ‘chernozems’ of Russia and the ‘prairie soil’ of the United States. It is derived from 2 types of rocks, the Deccan and the Rajmahal trap and forriginous gneisses and schists occurring in the Tamil Nadu state under semi-arid conditions. There is no change in colour upto a thickness of 2 to 3 metres. They are sticky when wet. Due to contraction on drying, large and deep cracks are formed. They contain abundant iron, lime magnesia and alumina. They are poor in phosphorus, nitrogen and organic matter. In all regur areas, and in those derived from ferro-magnesium schists, in particular, there is a layer rich in kankar nodules formed by the segregation of calcium carbonate. The soils are generally rich in montmorillonitic and beidellitic group of clay minerals. black carbon (BC): An impure form of carbon produced by incomplete combustion of fossil fuel and wood (forming soot) or biomass (forming charcoals). It exists in aerosols, sediments and soils. black earth: It is synonymous with “Chernozem;” to describe self-mulching black clays. (Not used in current U.S. system of soil taxonomy). blanching: To prevent from becoming green, by excluding light, as lettuce leaves or celery. blanket recommendations: Refers to the general term for fertilizer recommendations, which are given for a large area without taking into account the field to field differences in nutrient status. Example: 12060-60 kg/ha of N-P2O5-K2O for irrigated HYV cereals or 25 kg zinc sulphate/ha in light soils and 50 kg zinc sulphate/ha in heavy soils or 25-30 kg S/ha to oilseeds. Opposite of tailor-made or soil test based or site-specific recommendations. These form the

major piece of advice on fertilizer application in the absence of soil tests though these are less efficient than soil test based recommendations. Under the IPNS, these are scaled down to the extent that nutrients are supplied through organic manures and biofertilizers. Same as general recommendation. bleicherde: The light-coloured, leached A2 (E) horizon of podzol soils. blended fertilizer: When a fertilizer mixture prepared by mixing /blending uniform sized granules of different fertilizers under dry conditions so as to provide a compound fertilizer. It is usually tailor made for specific situations such as a large farm or a commercial plantation. blind cultivation: Cultivating with a harrow weeder, rotary weeder or other implements to kill weeds before a seeded or planted crop has come up. blizzard: A severe weather condition characterized by low temperatures and strong winds (greater than 35 mph) bearing a great amount of snow, either falling or blowing. When these conditions persist after snow has stopped falling, it is called a ground blizzard. bloat: Bloat is a digestive disorder characterized by an accumulation of gas in the first two compartments of a ruminant’s stomach (the rumen and reticulum). Production of gas (primarily carbon dioxide and methane) is a normal result of fermentation processes. The gas is usually discharged by belching (erutication) but, if the animal is unable to remove the excess gas, pressure builds up in the rumenreticulum exerting pressure on the diaphragm which prevents the animal from inhaling, and bloat occurs. The most common type of bloat is frothy bloat where gas builds up in a foam or froth above the rumen contents and the normal belching is inhibited. Bloat can occur on any forage that is low in fibre and high in protein but is most common on immature legume pastures. It usually occurs when cattle or sheep are first turned onto legume pastures. It seldom occurs on grasses, (or pastures with at least 50% grass), coarser pastures, or hay. Animals that are hungry or greedy feeders are most susceptible. blood meal: The dried, powdered blood used as a manure/ fertilizer. It is one of the highest nonsynthetic sources of nitrogen and if over-applied it can burn plants with excessive ammonia. It is derived from dried animal blood. Its typical composition is 10-12% N, 1.2% P2O5 and 1.0% K2O. Blood meal is

bone meal very soluble in water (unlike most other dry organic fertilizers). It also contains plant growth regulators. All this together means that its effect is strong and quick, but its power will only last a short while, especially in wet weather. Blood meal is completely soluble and can be mixed with water to be used as a liquid fertilizer. blown-out land: In soil survey a map-unit, which is a type of miscellaneous area from which most of the soil has been removed by wind erosion. The areas are generally shallow depressions with flat, irregular floors, which in some instances have a layer of pebbles or cobbles. blowout: A hollow or depression of the land surface, which is generally saucer or trough-shaped, formed by wind erosion especially in an area of shifting sand, loose soil, or where vegetation is disturbed or destroyed. blue baby syndrome: An illness that begins when large amounts of nitrates in water are ingested by an infant and converted to nitrite by the digestive system. The nitrite then reacts with oxyhaemoglobin (the oxygen-carrying blood protein) to form methemoglobin, which cannot carry oxygen. If a large enough amount of methemoglobin is formed in the blood, body tissues may be deprived of oxygen, causing the infant to develop a blue colouration of their mucous membranes and possibly digestive and respiratory problems. This condition is also known as methemoglobinemia. blue green algae (BGA): BGA or cyanobacteria (Greek ‘Kyanos’ meaning blue) are filamentous, photosynthetic, aerobic N fixing organisms. The role in paddy fields was first reputed by P.K. De in 1939. More than 100 species of BGA are known to fix N. Commonly occurring BGA are Nostoc, Anabaena, Aulosira, Tolypothrix, Calothrix etc. These are used as biofertilizer for wetland rice (paddy) and can provide 25-30 kg N/ha. They also secrete hormones like IAA, GA and improve soil structure by producing polysaccharides, which help in the binding of soil particles resulting in better soil aggregation. BGA need all the plant nutrients for their growth and N-fixation. Optimum temperature for BGA is about 30-35ºC and low temperature decreases their growth. The optimum pH for BGA growth in culture media ranges from 7.5 to 10.0 and its lower limit is about 6.5-7.0. BGA inoculum can be prepared in the laboratory or in the open fields. Under laboratory

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conditions, BGA inoculum can be prepared in nutrient medium in glass containers or small tanks, which is efficient but energy intensive and expensive. Recommended rate of inoculation in the rice field is 10 kg BGA flakes/ha. bog iron ore: Impure ferruginous deposits developed in bogs or swamps by the chemical or biochemical oxidation of iron carried in solution. bog soil: A great soil group of the intrazonal order and hydromorphic suborder. Includes muck and peat. bog: A peat-accumulating wetland that has no significant inflows or outflows and supports acidophilic mosses, particularly Sphagnum. bog: A shrub peatland dominated by shrubs, sedges, and peat moss and usually having a saturated water regime or a forested peatland dominated by evergreen trees (usually spruces and firs) and/or larch. Bogs have a high water table maintained directly by rain and snow. Bogs are characterized by acid-loving vegetation, and are often typified by the dense surface cover of aquatic moss. boiling point: The temperature at which the vapour pressure of a liquid equals the pressure of its surface. The liquid will than vapourize. If the pressure of the liquid varies, the actual boiling point varies. For water the boiling point is 100 degrees Celsius. bole: (i). Tree stem once it has grown to substantial thickness, capable of yielding timber or large poles.(ii). The trunk of a tree. It may extend to the top of the tree as in some conifers, or it may be lost in the ramification of the crown, as in deciduous species. boliland rice (Sierra Leone): Rice grown in fields that may be flooded for 2-4 months. bolting or shooting: Refers to significant stem elongation that precedes flowering in many plants. bone ash: A product obtained by burning bones to ash. The material contains 30 to 40% P2O5. bone meal: A mixture of crushed and coarsely ground bones that is used as an organic fertilizer for plants and in animal feed. As a fertilizer, bone meal is primarily used as a source of phosphorus. Raw bone meal consists of ground bones without any of the gelatin or glue removed. It contains at least 3% N and about 22% P2O5 of which about 8% is citrate soluble (available). Also contains variable amounts of micronutrients. Steamed bone meal is obtained by treating crushed bones with steam under pressure

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B

bone superphosphate

in order to dissolve part of gelatin and then grinding the residue. It contains about 28% P2O5 of which about 16% is citrate soluble (available). It can be obtained as a powder by grinding the crushed bones and then passing them through a 1 mm mesh. Being relatively slow-acting, bone-meal should not be used as a top-dressing; it must be incorporated into the soil in order to become available. It may be applied either at sowing time or a few days before sowing and should be broadcast. It is particularly suitable for acid soils. In some parts of the country, charred and powdered bones are used as a manure. Charring destroys about half the nitrogen, but leaves intact practically the whole of P2O5 in a quickly available form. Bone meal once was often used as a dietary calcium supplement. Research in the 1980s found that many bone meal preparations were contaminated with lead and other toxic metals, and it is no longer recommended as a calcium source. bone superphosphate: Ground bone or bone meal that has been treated with sulphuric acid. Contains 1-2% N and 16% P2O5 of which about 50% is water soluble (available). Commercial production of fertilizer SSP started in the 19th century with the use of bones as the raw material for P rather than phosphate rock. boom: An elevated, cantilevered sprinkler(s) mounted on a central stand. The sprinkler boom rotates about a central pivot. boot stage: Growth stage of grasses (cereals) at the time the head is enclosed by the sheath of the uppermost (flag) leaf. booting: State of plant growth, especially in cereals, indicated by swelling of the flag leaf. boralfs: Alfisols that have formed in cool places. Boralfs have frigid or cryic but not pergelic temperature regimes, and have udic moisture regimes. Boralfs are not saturated with water for periods long enough to limit their use for most crops. borax: Sodium tetraborate compound. Formula Na2B4O7.10H2O. Contains 10.5% B. An important boron fertilizer for soil or foliar application. border dikes irrigation: Earth ridges built to guide or hold irrigation water within prescribed limits in a field; a small levee. border ditch irrigation: A ditch used as a border of an irrigated strip or plot, water being spread from one or both sides of the ditch along its entire length.

border irrigation: A sub-system of controlled flood irrigation in which the land is divided into parallel border strips demarcated from one another by earth ridges. Water is successively delivered into each strip from a head or field ditch at its upper end. On the upstream part of each strip is a flat zone, the level portion from which the stream of water spreads evenly across the entire downstream portion. border-strip irrigation: The field is divided into number of stripes by forming bunds of around 15 cm height. These parallel earth ridges are called borders, and are formed to guide a sheet of flowing water across a field. The area between two borders is the border strip. Length of the strip ranges from 30 to 300 m and width from 3 to 15 m. However, the most common sizes are 60 to 90 m in length and 6 to 12 m in width. The size of border strips depend on stream size, soil structure and slope of the land. The borders are laid out along the general slope or on the contour. Water from the channel is allowed into each strip at a time. This method is suitable for close growing crops and medium to heavy textured soils, but not suitable for sandy soils. boreal forest: High to mid-latitude biome dominated by coniferous forest. Predominant vegetation of this biome is various species of spruce, fir, pine, and cedars. Also called Taiga. boro rice: An irrigated, high-yielding, cold-tolerant, relatively pest-free and photoperiod-insensitive rice cultivated during the winter months in India and Bangladesh. Generally transplanted in DecemberJanuary and harvested in April-May. borolls-mollisols: With a mean annual soil temperature of 400 g kg-1 unless they have a calcic horizon, and they are not saturated with water for periods long enough to limit their use for most crops. boron (B): Its essentiality for plants was established by K Warrington in 1923. Soil boron is mostly derived from basaltic and granite rocks, limestones, sandstones, shales etc. with shales being the richest (100 ppm B) and basaltic rocks with 5 ppm B being the poorest. Absorbed by plant roots as H 3 BO 3 . Usual concentration in plant dry matter is 20-30 ppm. boron fertilizers: Sources of boron, which are used to provide B for crop nutrition. Example: Sodium

braided stream tetraborate or borax Na2B4O7.10H2O (10.5% B), Boric acid H3BO3 (17% B), Solubor Na2B4O7.5H2O + Na2B10O16.10H2O (19% B), boron frits etc. boronated SSP: Single superphosphate (SSP) which has been fortified with boron, usually to contain 0.2% B along with 16% P2O5. Targeted for areas requiring the application of both P and B and also for facilitating the ease and uniform application of small amounts of B to be applied. boron-critical level: It is the concentration of B in soils or plants below which the soil/plant is considered deficient in B and a significant response to its application can be expected. Level of boron associated with 90% of maximum yield. The critical level depends on the soil, crop, cultivar and yield potential. Commonly, the critical level of B in soils is taken as 0.5 ppm hot-water soluble B and 20 ppm B in plant dry matter. boron-deficiency: It’s deficiency causes a physiological disorder affecting plants grown on low boron soils. Boron deficiency symptoms first appear at the growing points. This results in a stunted appearance (rosetting), barren ears due to poor pollination, hollow stems and fruit (hollow heart), brittle discoloured leaves, and loss of fruits and nuts. Young leaves are deformed and arranged in a cluster (rosette), there may be cracking and cork formation in stalks, stems and fruits, thickening of stems and leaves, shortened inter-nodes, dying of the growing points and reduced bud, flower and seed production. Other symptoms are early seed or fruit drop, hollow heart in groundnut, unsatisfactory pollination and poor translocation of photosynthates etc. Boron deficiencies are mainly found in acid soils, on sandy soils in regions of high rainfall or under irrigation, and those soils with low soil organic matter. Borate ions are mobile in soil and can be leached from the root zone. Boron deficiencies are more pronounced during drought periods when root activity is restricted. Crop-specific symptoms include; (i). Beetroot- rough, cankered patches on roots, internal brown rot. (ii). Cabbage- distorted leaves, hollow areas in stems. (iii). Cauliflower- poor development of curds, and brown patches. Stems, leafstalks and midribs roughened. (iv). Celery- leaf stalks develop cracks on the upper surface, inner tissue is reddish brown. Boron deficiency can be avoided by improving the moisture retaining capacity of light soils, and ensuring pH is kept below 7. Borax can be added to the soil.

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boron-functions: A primary function of boron is related to cell wall formation, so boron-deficient plants may be stunted. Sugar transport in plants, flower retention and pollen formation and germination also are affected by boron. Seed and grain production are reduced with low boron supply. boron-toxicity: Stage associated with undesirable effect of excess B in soils or plants. It can be a problem in arid/semi-arid regions or where excessive boron gets applied through fertilizer or through B-rich irrigation waters. Symptoms of B toxicity are yellowing of the leaf tip followed by gradual necrosis of the tip and leaf margins which spread towards the midrib. Leaves become scorched and drop early. In water quality rating, waters containing below 1.0 ppm B have low B toxicity hazard while those above 4.0 ppm B have very high B toxicity hazard. botanical pesticides: Pesticides whose active ingredients are plant-produced chemicals such as nicotine, rotenone, or strychnine. Also called plantderived pesticides. Being natural pesticides, as distinct from synthetic ones, they are typically acceptable to organic farmers. boulder clay: Unstratified glacial deposits laid down directly beneath the ice or dropped from the surface as the ice melted; boulder clay and till are synonymous terms for this unsorted material which ranges from rock flour to rocks and boulders of great size, according to the nature of the bedrock. bouyoucos moisture meter: An equipment used for measuring the soil moisture ‘in situ’ with the help of gypsum block or nylon block fixed in field. It was invented by the scientist Bouyoucos. brackish water: Refers to water, which is saline/ salty due to excessive concentration of salts in it. Can be saline, sodic (high in Na) or saline-sodic. Usually unfit for irrigation, especially for salt sensitive plants. Waters high in boron are not suitable for irrigation as their use can lead to boron toxicity but can be used if diluted with normal water. bradyrhizobium: It is name of a new genus of erstwhile Rhizobium, which is slow growing. Important in tropical legumes. Example: Bradyrhizobium japonicum. braided stream: A channel or stream with multiple channels that interweave as a result of repeated bifurcation and convergence of flow around interchannel bars, resembling (in plan view) the

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B

brake crops

strands of a complex braid. Braiding is generally confined to broad, shallow streams of low sinuosity, high bedload, non-cohesive bank material, and a steep gradient. brake crops: These crops are grown to break the continuity of the agro-ecological situation of the field under multiple cropping systems. The inclusion of such crops in the cropping system helps to reduce the inoculum of soil-borne harmful biotic agents such as weeds, pests, pathogens and parasites and improves soil conditions for crop growth. Growing potato, pulses or oilseeds in continuous cereal cropping systems, for instance rice-rice, rice-wheat, rice-maize breaks the continuity of a large number of pests due to variations in host ranges and changing of agro-ecological situations. Brake crops are also used to designate guard crops particularly those, which help to brake the wind speed and protect crop plants from wind hazards. branching habit in cotton: This refers to the behaviour of branches produced by cotton plants like the vegetative branches (monopodial) or fruiting branches (sympodial). The plants bearing more monopodial branches show the longer duration of the variety but more of sympodial branches show a shorter duration and higher yield potentials. Thus the latter plant type should be preferred over the first one. bray P1 extraction reagent: An extraction reagent of 0.03N ammonium fluoride (NH 4F) in 0.025 N hydrochloric acid (HCl) for determining soilextractable phosphorus(P) in acid soils of moderate cation exchange capacity(CEC). bray P2 extraction reagent: An extraction reagent of 0.03N ammonium fluoride (NH 4 F) in 0.1 N hydrochloric acids (HCl) for determining soilextractable phosphorus(P) in acid soils of moderate cation exchange capacity(CEC) that have been either fertilized with rock phosphate or that have sizable content of calcium phosphate. bray’s nutrient mobility concept: As the mobility of a nutrient in the soil decreases, the amount of that nutrient needed in the soil to produce a maximum yield (the soil nutrient requirement) increases. break even point: The point where increase in crop yield just offsets input costs. A no profit - no loss point. Example: if the application of a fertilizer worth Rs.500 produces extra crop worth Rs.500, then it is a break even point where the extra output only pays

for the input. Net profit starts accruing only above the break even point. Represented by VCR = 1. breakthrough curve: The relative solute concentration in the outflow from a column of soil or porous medium after a step change in solute concentration has been applied to the inlet end of the column, plotted against the volume of outflow (often in number of pore volumes). breccia: A coarse grained, clastic rock composed of angular fragments (>2mm) bonded by a mineral cement or in a finer-grained matrix of varying composition and origin. brine: Highly salty and heavily mineralized water, containing heavy metal and organic contaminants. brix: It refers to the total solid in any solution but in case of sugarcane it is used for assessing the maturity of canes. The brix is measured by the help of hand refractometer and the values over 16 indicate that the canes are approaching maturity and they may be harvested for milling. broad bed and furrow (B.B.F.) system: A land management system for successful crop production in vertisols (heavy black soil) by providing better drainage through raised broad beds (about 90-100 cm wide) and furrow (25-30 cm wide). broad spectrum pesticide: A pesticide which is active towards a wide variety of weeds or other pests; often used to describe an antibiotic that is effective against a wide range of microorganisms. broadcast aman rice: Deepwater rice sown in March and April alone or mixed with aus and transplanted in May after boro rice is harvested. It grows in the monsoon floodwater with depths from 0.5 up to 4.0 m from June to September and generally harvested during November and December. Some of these rices are photoperiod-sensitive. broadcast application: Application of fertilizer involving spreading of fertilizer on the entire field, manually or by machine before planting or in the standing crop. It maximizes soil-fertilizer contact and hastens the rate of transformation of fertilizer in the soil. It can be made as a pre-plant (basal) application or as a top dressing. Top dressing is practiced mostly on dense crops not planted in rows or in dense rows (small grains) and on grassland. Broadcast application is also used when fertilizers should be incorporated into the soil after application to be effective (phosphate fertilizers), or to avoid

buffer strips evaporation losses of nitrogen (urea, diammonium phosphate). Incorporation through tilling or ploughing-in is also recommended to increase the fertility level of the entire plough layer. Whether the fertilizer is broadcast by hand or with fertilizer spreading equipment, the spreading should be as uniform as possible. broadcast planting: A method of planting in which the seeds or seedlings are dropped or thrown over the entire surface area of the field. broadcast tillage (total surface tillage, full-width tillage): Manipulation of the entire surface area by tillage implements as contrasted to partial manipulation in bands or strips. broadcast: Application of solid or liquid fertilizer or other agrochemical on the soil surface. Usually done prior to planting and normally incorporated with tillage but may be unincorporated in no-till systems. broadcasting: The action of spreading seeds, fertilizer, or pesticides on the surface of the field at random, by hand or by machine. broadleaf weeds: Used in weed terminology to designate a broad group of non-grass like plants, usually dicots. bronzing: Development of bronze/copper colouration on the plant tissue. A common nutrient deficiency symptom. broth: A suspension of microorganism cultures, very common in a biofertilizer laboratory, e.g. Rhizobium broth, Azotobacter broth etc. Good broth quality is represented by cell counts ranging from 109 to 1010 ml. brown earths: Soils with a mull horizon but having no horizon of accumulation of clay or sesquioxides. brown forest soils: A great soil group of the intrazonal order and calcimorphic suborder, formed on calciumrich parent materials under deciduous forest, and possessing a high base status but lacking a pronounced illuvial horizon. brown podzolic soils: A zonal great soil group similar to Podzols but lacking the distinct A2 (E) horizon characteristic of the Podzol group. brown rice: Rice grain with its hulls removed but not polished. brown soils: A great soil group of the temperate to cool arid regions, composed of soils with a brown surface and a light-coloured transitional subsurface horizon over calcium carbonate accumulation.

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browse: Leaves, small twigs and shoots of shrubs, seedling and sapling trees, and vines available for forage for livestock and wildlife. browsing: The feeding on the aboveground parts of trees and shrubs (buds, shoots and leaves) by livestock or wild animals. brush: (i). Undergrowth, often of a thicket and including the small trees and shrubs. (ii). Materials such as twigs cut from undergrowth. Bt crops: Crops that have been genetically engineered to carry the gene from the soil bacterium Bacillus thuringiensis. This bacterium produces a protein that is toxic when ingested by certain moth and butterfly caterpillars that are destructive to crops. Crops containing the Bt gene are able to produce this toxin, thereby providing protection throughout the entire plant. For example, Bt cotton is genetically engineered to provide protection exclusively against bollworms (pink bollworms), and other caterpillar pests. buffer pH: For making accurate lime recommendations, soil test laboratories must determine both the active and the potential acidity of a soil sample. The active acidity is determined by use of a pH meter and the potential acidity is determined by the buffer pH procedure. The buffer pH is the number shown under the heading “BpH” on the soil test report. This number is derived by adding a “buffer” solution to the soil sample after the normal soil pH is read. The pH meter is then used to measure the decrease in the pH of the buffer solution due to the H+ held by the soil. The change in pH of the buffer solution after it has been added to the soil and the water pH determine the lime requirement for the soil. There are numerous buffer solutions in use. The commonly used buffer solution is referred to as the SMP Buffer Solution. It has an initial pH of 7.5. buffer power: The ability of solid phase soil materials to resist changes in ion concentration in the solution phase. It includes pH buffering as well as the buffering of other ionic and molecular components. buffer strips: Contour strips of grass or other erosion resisting vegetation between or below cultivated strips or fields. Slender areas of permanent vegetation, often planted along the edge or the contour of a field, usually to slow the flow of water or the velocity of wind, in order to trap sediment and other materials (nutrients, pesticides, and certain

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B

buffer zone management (BZM)

pathogens) before they leave the farm and become pollutants. Types of buffers include filter strips, field borders, grassed waterways, field windbreaks, shelterbelts, contour grass strips, and riparian buffers. Also called conservation buffers. buffer zone management (BZM): A process with the objective of optimizing the political, economic, social, cultural, ecological and intrinsic value of resources. The objective is reached through active, adaptive management, with fairness to all groups, and by allowing for changing values over time. buffer zone: An area around a forest, national park, or any other conserved place that provides the local community with products that they would otherwise take from the forest, or that provides an opportunity to produce alternative products. buffer: A medium, which resists change or a substance added to resist change in concentration or pH activity in a solution. Example: If a large change in applied K results in a small change in solution K, the soil is said to be well buffered with respect to K. buffering capacity: Refers to the ability of a medium to resist change in concentration or activity of its constituents and its properties in response to external intervention. High buffering capacity of a soil is associated with high content of organic matter, silt and clay. Sandy soils or those having low organic matter content have low buffering capacity. bulbs and tubers: A commodity class for dormant underground parts of plants intended for planting (includes corms and rhizomes). bulk area: The total area, including solid particles and pores, of a cross-section through an arbitrary quantity of soil; the area counterpart of bulk volume. bulk blended fertilizer: A fertilizer mixture prepared without a chemical reaction from components that retain their physical form. Supplied in bulk, usually prepared shortly before use and often granular. Bulk blends may or may not contain micronutrients but offer a practical route for uniform application of small amounts of micronutrients if these can be properly blended with major nutrient carriers. bulk density (soil): Mass per unit bulk volume (including pores) of soil or particle that has been dried to constant weight at 105°C. The value is expressed as Mg per cubic meter (Mg m-3). It is favourable to have a low bulk density so that water and air can move through the soil. The optimal bulk

density depends on soil texture. Soil compaction causes the bulk density to increase, whereas any practice that improves soil tilth decreases bulk density. Soil tillage temporarily decreases bulk density, after which the soil recompacts to similar (or greater) densities as a no-till soil at the end of the growing season. bulk fertilizer: Fertilizer in a stockpile or transported loose, without any form of packaging or closed container. bulk length: The total length, including solid particles and pores, of a straight-line path through the soil; the length counterpart of bulk volume or bulk area. bulk specific gravity: The ratio of the mass of a unit volume of dry soil to the mass of the same unit volume of water. bulk volume: The volume, including the solids and the pores, of an arbitrary soil mass. The bulk volume is determined before drying to constant weight at 105° C. bulky organic manure: Term used collectively for cattle dung, farmyard manure (FYM), composts etc. because of their large bulk in relation to the nutrients contained in them. bund: A low embankment, wider than a ridge, normally higher than 20 cm but lower than 1 m, used to control runoff on an irrigated land. Bunds are characterized by the materials used (‘earth bund’, ‘stone bund’ or ‘mixed bund’), their shape (‘triangular bund’, ‘trapezoidal bund’, ‘semi-circular bund’), their dimension (‘large semi-circular bund’), and their position across the slope (‘contour bund’, ‘graded water diversion bund’, ‘straight water diversion bund’) and presence of ties if any (‘tied bund’). buried soil: Soil covered by an alluvial, loessal, or other surface mantle of more recent depositional material, usually to a depth greater than 50 cm. bush fallow: The natural vegetation that arises when land is left uncultivated for some time. Composed of small trees, shrubs, grasses (and sedges) and herbaceous plants. Bush fallow may be grazed or browsed and firewood collected from it before it is returned to cultivation. bush: (i). A general term for low tree–high grass vegetation occurring in semi-arid or seasonally arid regions. Can be further described by the dominant species present, for example, ‘acacia bush’, ‘combretum bush’. (ii). A low, well-branched shrub.

calcitic limestone by-product: (i). A substance obtained during the manufacture of another substance, e.g. bran is a byproduct of milled rice. (ii). Any substance (formed in a process) or remaining after the main product has been obtained. It is of lesser value than the main product. Example: press mud in a sugar factory, basic slag in a steel plant, phospho-gypsum in a phosphoric acid plant, oilcakes after oil extraction from seeds etc. Several by-products are valuable sources of plant nutrients and can be gainfully used in supplying plant nutrients for crop production as a part of IPNS.

C cadmium (Cd): A toxic heavy metal. Atomic weight 112.4. Usual content in soils is 0.4 ppm. Can enter finished fertilizers through phosphate rock, which is an important raw material and other sources. Potentially toxic to plants and animals. It is a heavy metal of greatest concern to human health. Associated with crippling condition known as Itai-Itai (Japanese) in humans. Rock phosphates can contain a wide range of cadmium content. caffeine: Is the purine base alkaloid found in tea and coffee which works as a stimulant. cairns group: A coalition of 17 agricultural exporting countries, formed in 1986 at Cairns, Australia, for the purpose of influencing the outcome of agricultural negotiations in the Uruguay Round of multilateral trade negotiations. During those negotiations and subsequently in the Doha Development Agenda negotiations, the Cairns Group has pressed WTO member countries to eliminate agricultural export subsidies, and to substantially reduce agricultural tariffs and trade-distorting farm subsidies. Members are Argentina, Australia, Bolivia, Brazil, Canada, Chile, Colombia, Costa Rica, Guatemala, Indonesia, Malaysia, New Zealand, Paraguay, the Philippines, South Africa, Thailand, and Uruguay. caking (fertilizer): (i). The agglomeration of fertilizer particles by adhesion at their points of contact to form a compact mass that is difficult to break up. (ii). A process by which a fertilizer loses its desirable free-flowing property. The principal reason for caking is change of moisture content. It is a sign of deterioration in physical quality. Use of anti-caking agents can help to minimize caking.

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calcareous soil: A type of soil containing sufficient free CaCO3 and other carbonates to effervesce visibly or audibly when treated with cold 0.1M HCl. These soils usually contain from 10 to almost 1000g kg-1 CaCO 3 equivalent. An easy way to check for calcareous soils is to add hydrochloric acid to the soil. If free carbonates are present, the acid will produce bubbling due to the evolving of CO2 gas. Calcareous soils have 100% base saturation, and the exchange complex is dominated by calcium. The pH of calcareous soils is from 7.0 to 8.2 due to the hydrolysis of calcium carbonate, which produces the strong base, calcium hydroxide, and the weak acid, carbonic acid. calcic horizon: A mineral soil horizon of secondary carbonate enrichment that is >15 cm thick, has a CaCO3 equivalent of >150 g kg-1, and has at least 50 g kg-1 more calcium carbonate equivalent than the underlying C horizon. calcids: Aridisols that have a calcic or petrocalcic horizon that has its upper boundary within 100 cm of the soil surface. calcification: It is a process or processes of soil formation in which the surface soil is kept sufficiently supplied with calcium to saturate the soil cation exchange sites, or the process of accumulation of calcium in some horizon of the profile, such as the calcic horizon of some aridisols and mollisols. calcifuge: It is a plant that does not tolerate alkaline (basic) soil. The word is derived from the Latin ‘to flee from chalk’. These plants are also described as ericaceous, as the prototypical calcifuge is the genus Erica (heaths). calciphytes: Plants that require or tolerate considerable amounts of calcium, or are associated with soils rich in calcium. calcite: A mineral, which occurs in nature. Pure calcite is 100% calcium carbonate (CaCO 3), which is crystallized, in hexagonal form. Calcite is a common constituent in calcitic limestone, dolomite, marble, chalk, marl, seashells, and similar substances. Because the mineral calcite is pure CaCO3, it is the standard by which the acid-neutralizing capability of all other liming materials is measured. calcitic limestone: Limestone containing mostly CaCO3. This term widely used by agronomists when referring to agricultural limestone with high calcium

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C

calcium (Ca)

content. It contains mainly calcium carbonate but may also contain small amounts of magnesium carbonate. The term is not as restrictive in definition as calcite. It is often used to distinguish materials of low magnesium carbonate content from those of high content, the latter being referred to as dolomitic limestone. calcium (Ca): An alkali metal, which is one of the essential plant macronutrients. Carl Sprengel established its essentiality for plants in 1839. Plant roots absorb it as the divalent cation Ca2+. Normal concentration of Ca in plant dry matter is 0.2-1.0%. Calcium as calcium pectate is a part of the structure of cell walls and membranes, is involved in root growth and elongation, cell division and activation or inhibition of enzymes. It is required for nodule formation and activates nitrogen fixers in soil and hence nitrogen fixation. Excessive amounts of Ca in the soil can decrease the availability of many micronutrients. calcium ammonium nitrate (CAN): A mixture of ammonium nitrate and finely pulverized limestone or dolomite, granulated together. It contains 21 to 26% nitrogen, half of which is in the form of ammonical nitrogen and the other half in the form of nitrate nitrogen. Its use does not make the soil acid by virtue of the calcium in it. calcium carbonate equivalent (CCE): Expression of the acid-neutralizing capacity of a carbonate relative to that for pure CaCO 3 , e.g., calcite; expressed as a percentage. The value for pure calcite is 100%; for pure dolomite, 108.5%. CCEs of most limestones vary from these percentages due to impurities in the rock and the fact that commercially available limestones are usually composed of mixtures of calcite and dolomite rather than either compound in its pure form. calcium carbonate: Mineral of Ca with calcite (CaCO3) as the main ingredient. Source of lime and Ca. Key constituent of agricultural limestone. It should not be mixed with urea, as doing so will lead to loss of N. calcium cyanamide: A compound containing 21% N in the amide and cyanide forms. Its formula is CaCN2. In soil, it is first converted to urea in the presence of water, and during the conversion, certain toxic products can be formed, which suppress weed growth. Because of the production of plant-toxic components, it must be applied so that the conversion to urea is completed prior to planting.

calcium fertilizers: Commercially available materials of acceptable quality which are used to provide calcium to soils and plants. It includes calcium oxide (50-68% Ca), dolomite (24-32% Ca) and gypsum (23% Ca). calcium nitrate: A compound containing N and Ca. Its formula is Ca(NO 3) 2 . Commercial product contains about 15% N and 28% CaO. Approximately two-thirds of world calcium nitrate fertilizer is used in Europe, but use is expanding in other parts of the world. It is extremely hygroscospic, which presents application difficulties, but the 100 per cent watersoluble nitrate form makes this relatively lowanalysis fertilizer attractive for use in high-value crops such as vegetables. calcium-critical level: Concentration of Ca in soils or plants below which the soil/plant is considered deficient in Ca and a significant yield increase to its application can be expected. Level of Ca, which is associated with 90% maximum yield. It depends on the soil, crop, cultivar and yield potential. Commonly the critical limit of Ca in soils is taken as less than 25% of CEC occupied by exchangeable Ca or less than 1.5 me exchangeable Ca/100 g soil. In plants, it can vary from 0.2% to several folds this value. calcium-deficiency: Calcium is taken up by plants as the divalent cation, Ca2+. Calcium deficiency is not likely for most crops when the soil is properly limed to adjust soil pH to optimum levels for crop production. As soils become more acidic, crop growth is often restricted by toxic soil concentrations of aluminum and/or manganese; not a calcium shortage. Calcium deficiency is observed first on the growing tips and youngest leaves. Such leaves become small, distorted, cup-shaped, crinkled and dark green. Terminal buds may deteriorate and die in fruit trees, root growth is severely impaired, groundnut shells may be hollow or poorly filled due to poor kernel development and new leaves in maize plants may fail to unfold. Symptoms of deficiency may also include: (i) slow root development. Roots may develop a dark colour and in severe cases the growing point may die. (ii) new leaf growth may slow and leaf tips may stick together. Remember that calcium does not readily translocate within the plant so deficiency symptoms will appear on the new growth. (iii) poor nodulation by nitrogen fixing bacteria on leguminous plant roots. Ineffective nodules are white to grayish green inside while healthy nodules have

capillary porosity dark pink interiors. (iv) blossom end rot in tomatoes. Calcium and proper water management improve plant resistance to this problem. (v) aborted and shriveled fruit on peanuts. A shortage of calcium at “pegging” results in a high percentage of “pops”. (vi) darkened plumule or “black heart” in peanut seed. This reduces yield, quality and crop value. (vii) pod rot diseases on peanuts. Pods are predisposed to fungus infections when calcium is deficient or out of balance with Mg and K. Calcium deficiencies are most likely to occur in acid, sandy soils from which calcium has been leached by rain or irrigation water. It may also occur in strongly acid peat and muck soils where total calcium is low. calcium-functions in plants: Calcium improves the absorption of other nutrients by roots and their translocation within the plant. It activates a number of plant growth-regulating enzyme systems, helps convert nitrate-nitrogen into forms needed for protein formation, is needed for cell wall formation and normal cell division, and contributes to improved disease resistance. Calcium, along with magnesium and potassium, helps to neutralize organic acids, which form during cell metabolism in plants. calcium-functions in soils: In soil, calcium replaces hydrogen (H) ions from the surface of soil particles when limestone is added to reduce soil acidity. It is essential for microorganisms as they turn crop residues into organic matter, release nutrients, and improve soil aggregation and water holding capacity. Calcium helps enable nitrogen-fixing bacteria that form nodules on the roots of leguminous plants to capture atmospheric nitrogen gas and convert into a form that plants can use. calibration curve: A graph, which depicts the effect of increasing rates of an independent variable on a dependent variable. Example: soil test crop response calibration, which helps to relate a given soil test value with the associated crop yield and hence guides the optimum nutrient application rate. calibration of sprayer: A series of steps done primarily to determine the volume of spray solution and time needed to spray a given area of field considering other factors (e.g., swath of the sprayer, pressure exerted inside the sprayer, or the sprayman’s walking speed at an even pace). calibration: Adjustment of model parameters to obtain model behaviour that corresponds with observed behaviour.

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caliche: (i). A zone near the surface, more or less cemented by secondary carbonates of Ca or Mg precipitated from the soil solution. It may occur as a soft thin soil horizon, as a hard thick bed, or as a surface layer exposed by erosion. (ii). Alluvium cemented with NaNO3, NaCl, and/or other soluble salts in the nitrate deposits of Chile and Peru. calorie: Quantity of energy. Equals the amount of heat required to raise 1 gram of pure water from 14.5 to 15.5°C at standard atmospheric pressure. cambic horizon: A mineral soil horizon that has a texture of loamy very fine sand or finer, has soil structure rather than rock structure, contains some weatherable minerals, and is characterized by the alteration or removal of mineral material as indicated by mottling or gray colours, stronger chromas or redder hues than in underlying horizons, or the removal of carbonates. The cambic horizon lacks cementation and has too few evidences of illuviation to meet the requirements of the argillic or spodic horizon. cambids: Aridisols that are not in cryic temperature regimes and do not have the following diagnostic subsurface horizons or features: argillic, salic, duripan, gypsic, petrogypsic, calcic, petrocalcic. canopy: The assemblage or volume of leaves of all ages supported by branched stems that form the photosynthetic layers of a tree or crop. capacity factor: Total quantity of a nutrient in the soil which is in form(s) that can be solubilised, desorbed and transferred into the soil solution when the latter is being depleted through plant uptake or by other means. Practically, the nutrient reserve, which can move into the soil solution during a crop’s life span. The reservoir of a nutrient, which supports the intensity factor. capillary action: Movement of water along microscopic channels. This movement is the result of two forces: the adhesion and absorption of water to the walls of the channels; and cohesion of water molecules to each other. capillary fringe: A zone in the soil just above the plane of zero gauge pressure that remains saturated or almost saturated with water. The extent can be inferred from the retentivity profile and depends upon the size-distribution of pores. capillary porosity: The small pores, or the bulk volume of small pores, which hold water in soils against a tension usually >60 cm of water.

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capillary rise

capillary rise: The upward movement of water through a soil caused by molecular attraction between water and soil particles. Dry soils can act like a sponge to bring groundwater to the surface.

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capillary water: Water that moves horizontally and vertically in soils by the process of capillary action. This water is available for plant use, usually with a tension >60 cm of water. carbon (C): It is a major plant nutrient having an atomic weight of 12. Constituent of carbon dioxide gas (CO2), which is one of the gases in the air and used by plants as a source of C for photosynthesis. Constituent of all organic compounds. Glucose or sucrose are used as C-source by many heterotrophic organisms while CO2 is used as C-source by photosynthetic organisms such as BGA and green plants. It is a key constituent of carbohydrates, proteins, fats, in fact all organic compounds including urea, soil organic matter, carbonates, bicarbonates etc. carbon cycle: (i). After plants take CO2 from the atmosphere, they split apart the C and O2 using energy from photosynthesis and creat C to C bonds of organic molecules. The plant uses some of these organic compounds for energy (respiration) and the C is returned to the atmosphere as CO 2 . The remaining organic compounds are incorporated into the plant itself, but are eventually added to the soil as plant liter or root deposition. Carbon in plant materials that are eaten by animals is released as CO 2 gas, manure, and body tissue. Organic C deposited into the soil by plants and animals is metabolized by soil organisms and the C is eventually returned to the atmosphere as CO2. Small amounts of CO2 reacts with water in the soil to form carbonic acid (H 2 CO 3 ), or with other cations to form carbonates and bicarbonates (e.g., Ca, K Mg). Bicarbonates are very soluble and mobile in the soil, and eventually, most of these bicarbonates and carbonates release the C as CO2 to the atmosphere. Some organic C comounds in the soil ave very resistant to decomposition and can reamin in the soil for a long time. This recalcitrant organic C accumulates in the soil to build up soil organic matter. (ii). The process of cyclic circulation of carbon from the bodies of microbes, plants and animals into the air and back again. In this sequence of transformation, CO2 of the air is fixed in living organisms by photosynthesis or by chemosynthesis, then liberated by respiration as well as by the death and

decomposition of the fixing organisms and ultimately returned to the atmosphere in its original state. carbon dioxide equivalent: A metric measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as “million metric tons of carbon dioxide equivalents (MMTCO2Eq).” The carbon dioxide equivalent for a gas is derived by multiplying the tonnes of the gas by the associated GWP. The use of carbon equivalents (MMTCE) is declining. carbon dioxide fertilization: An expression (sometimes reduced to ‘fertilization’) used to denote increased plant growth due to a higher carbon dioxide concentration. Depending on their mechanism of photosynthesis, certain types of plants are more sensitive to changes in atmospheric CO 2 concentration. In particular, C3 plants generally show a larger response to CO2 than C4 plants. carbon intensity: The amount of carbon by weight emitted per unit of energy consumed. A common measure of carbon intensity is weight of carbon per British thermal unit (Btu) of energy. When there is only one fossil fuel under consideration, the carbon intensity and the emissions coefficient are identical. When there are several fuels, carbon intensity is based on their combined emissions coefficients weighted by their energy consumption levels. carbon sequestration: Retention or fixing of carbon in ways that prevent or delay its emission to the atmosphere as carbon dioxide. This may help mitigate climate change by reducing its amount in the atmosphere. Silvicultural practices that encourage rapid, long-term tree growth are an example as large amounts of carbon fixed through photosynthesis is tied up in the tree biomass. Crop residue retention practices designed to prevent erosion and improve the productivity of soil, also retain larger amounts of carbon compared to many traditional cultivation practices. carbon sink: A process or activity that absorbs, or takes up, released carbon from another part of the carbon cycle. The four types of sinks, within which carbon behaves in a systematic manner, are the atmosphere, the terrestrial biosphere (including agricultural, forest, and freshwater systems); oceans, and sediments (including fossil fuels). carbon: sulphur (C:S) ratio: It is the ratio of organic carbon to sulphur in organic materials, soils etc. At

catalyst C:S ratio of less than 200, net mineralization (release) of organic S is expected in the soil while a C:S ratio higher than 400 favours net immobilization (tying up) of mineral S. carbon:nitrogen (C:N) ratio: It is the ratio between organic C and N in organic materials or soils. When C:N ratio of crop residues is below 20, there is a net gain (release) of mineral N, when it is above 30, there is a net immobilization of mineral N and the crop may even face a temporary N-deficiency. The C:N ratio in saw dust for example is 103:1, rice straw has 66:1 while FYM has 16:1. Thus FYM is a better manure than sawdust and rice straw. Narrow C:N ratio (below 20) favours mineralization. N-rich legume residues decompose faster than N-depleted cereal residues. carbon:phosphorus (C:P) ratio: It is the ratio between organic carbon and phosphorus in organic materials or soils. Net mineralization (release) of organic P results if the C:P is less than 200 and there may be net immobilization of P above C:P of 300. carboxylic acid: A carboxylic acid is an organic molecule with a -(C=O)-OH group. The group is also written as -COOH and is called a carboxyl group. The hydrogen on the -COOH group ionizes in water; carboxylic acids are weak acids. The simplest carboxylic acids are formic acid (H-COOH) and acetic acid (CH3-COOH). cardinal temperatures: Below a certain minimum and beyond maximum value of temperatures, plant growth ceases. Between these limits, there is an optimum temperature at which growth proceeds with greatest rapidity. These three points are known as cardinal temperatures. carrier concept: Refers to the movement of ions across the cell membrane by specific carriers (hypothetical) with the help of metabolic energy. carrier: (i). Substances used to contain and carry the cultures of microorganisms in a commercial biofertilizer product. Most of the biofertilizers except liquid biofertilizer are carrier based. Carriers giving acid reaction such as peat, lignite etc., depending on acidity, are neutralized through mixing with powered calcium carbonate. Example: peat, lignite, charcoal, rice husk, vermiculite, soil, coir dust, press mud and polymer compounds. (ii). A molecule which serves to carry a nutrient ion across the cell membrane. Such molecules (called ionophores) have

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a key role to play in active (energy-dependent) nutrient uptake by the plant roots. Example: valinomycin nonactin. carry over effect: The effect of an input (fertilizer or biofertilizer), which is expressed on a crop sown after the directly fertilized or inoculated crop. Important for P, S, Cu, Zn and biofertilizer management. It is an important aspect of nutrient management and economics since one application can benefit several crops in succession. carrying capacity: Represents the point of balance between reproduction potential and environmental resistance, that is the maximum population of a species that a specific ecosystem can support indefinitely without deterioration of the character and quality of the resource, i.e., vegetation or soil. It is expressed by numbers of livestock, numbers of certain wild animals, numbers of tourist visits, etc., per unit area. cartography: Art and science of the organization and communication of geographically related information such as a yield image into maps or charts. Field of knowledge that studies map construction. Act of creating a map. case study: The detailed study of an individual unit such as a household, farm, enterprise or activity. It contrasts with the survey approach in which a number of units are studied. The case-study approach is useful for purposes of familiarization and teaching whereas the survey approach is more oriented to gaining information about the population of relevant unit. casein: The major portion of milk protein, manufactured from skim milk and used in processed foods (such as dessert toppings and coffee whiteners) and in industrial products such as glue, paint and plastics. Casein may be blended with nonfat dry milk to produce milk protein concentrate. cash crops: These crop plants are grown for sale to earn hard cash. The processing of such crops after harvest is beyond the means of individual farmers, for instance jute, tobacco, cotton and sugarcane. cat clay: Poorly drained, clayey soils, commonly formed in an estuarine environment, that become very acidic when drained due to oxidation of ferrous sulphide. catalyst: A chemical or biochemical substance, which facilitates a reaction without actually undergoing any

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catch crop (=emergency crop or contingent crop)

permanent change itself. Example: urease is a catalyst in urea hydrolysis, nitrate reductase reduces nitrate to ammonia, nitrogenase is involved in biological nitrogen fixation.

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catch crop (=emergency crop or contingent crop): These are the crops, which are cultivated to ‘catch’ the forthcoming season. They replace a main crop that has failed due to biotic or climatic or management hazards and utilize the remaining period of the season. They provide livestock feed at a difficult time of the year, check weed growth, conserve soil, utilize added fertilizer and moisture. They are generally of very short duration, quick growing, fast bulking, harvestable or usable at any time of their field duration and adaptable to the season, soil and cultural practices, for instance mungbean, urdbean, cowpea, pearlmillet, spinach, radish, coriander, onion. category: Any one of the ranks of the system of soil classification in which soils are grouped on the basis of their characteristics. catena: A sequence of soils of about the same age, derived from similar parent material, and occurring under similar climatic conditions, but having different characteristics due to variation in relief and in drainage. cathode: The negative pole or electrode of an electrolytic cell or system. The cathode attracts positively charged particles or ions (cations). cation exchange capacity (CEC): (i). It is the capacity of a soil for ion exchange of positively charged ions between the soil and the soil solution. Cation exchange capacity is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination. The quantity of positively charged ions (cations) that a clay mineral or similar material can accommodate on its negatively charged surface, expressed as milli-ion equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are aluminosilicates in which some of the aluminum and silicon ions have been replaced by elements with different valence, or charge. For example, aluminum (Al3+) may be replaced by iron (Fe2+) or magnesium (Mg2+), leading to a net negative charge. This charge attracts cations when the clay is immersed in an electrolyte such as salty water and causes an electrical double layer. (ii). It is a measure of the total amount of exchangeable cations that can be held by a given mass of soil, expressed in me/100 g

soil (old term) or Cmol/kg (new term) at neutrality (pH 7) or at some other stated pH value. Soils differ in their capacity to attract and hold positively charged elements against the force of leaching. This capacity is governed by the type of clay and amount of organic colloids present in the soil. Montmorillonitic type clays have a higher net electrical charge than kaolinitic type clays; consequently, they have a higher cation exchange capacity. Soils containing a high percentage of organic matter also tend to have high cation exchange capacities. Sandy soils containing a low percentage of clay and organic matter have low exchange capacities. This explains why coarse textured soils require more frequent applications of lime and fertilizer than soils containing more clay and organic matter. cation exchange sites: Fractions of the surface of soil particles that exhibit the power to hold the positively charged cations. They occur at the surface of clay and organic colloids. They are more abundant in fine-textured soils having high contents of clay and organic matter than in sandy soils that are low in clay and organic matter. Calcium is held more firmly at the surface of soil colloids than potassium. cation exchange: The exchange of cations held at the surface of soil particles for other cations in the soil solution. Cations held on the surface of soil colloids and contained in the soil solution are available for plant use. Adsorbed cations, however, can be replaced by other cations present in the soil solution through the process of cation exchange. These replaced cations may then combine with an anion and be leached from the soil. For instance, when large amounts of a fertilizer material such as muriate of potash (KCl) are applied to the soil, the KCl when dissolved in soil moisture disassociates into K+ and Cl - ions. The potassium cations may replace adsorbed magnesium (Mg2+) cations. The replaced magnesium ions can then combine with Cl- ions to form magnesium chloride. This compound is soluble and can be leached from the soil when rain occurs. The force by which cations are held by soil colloids will depend upon several factors. The smaller the cation and the less water it has adsorbed, generally the tighter the cation is held on the soil particles. Hydrogen ions, therefore, are more tightly held and more difficult to replace than larger and more hydrated cations such as ammonium, calcium, magnesium, and potassium. Divalent cations (two charges) are

check-basin irrigation generally held tighter by soil colloids than monovalent cations (one charge). Therefore, calcium and magnesium which are divalent cations are more difficult to replace than the monovalent cations such as potassium and ammonium. cation: Positively charged atom or group of atoms; e.g. potassium (K+), ammonium (NH4+). cavitation: The formation of gas or water vapourfilled cavities in a liquid volume when the pressure is reduced (tension is increased) to a critical level. In water systems cavitation typically occurs at about 0.08 MPa of water tension. In confined systems, cavitation can create discontinuity of water columns preventing the non-elastic transmission of pressure along the column across the cavitation. ceilometer: An instrument that is used to measure the angular elevation of a projected light on the base of a cloud. It measures the angle of the cloud base included by the observer (or machine), the ceiling light and the illuminated spot on the cloud. cellulose decomposing microorganisms: Microorganisms, which have the ability to degrade plant residues (cellulose rich materials) in soil. These microorganisms can be utilized for hastening the process of composting. Example: Bacteria Cellulomonas biazotea, Achromobacter sp., fungi Trichoderma viride, Chaetomium globosum and Actinomycetes Thermonospora curvata, Nocardia sp. cemented: Having a hard, brittle consistency because the particles are held together by cementing substances such as humus, CaCO3, or the oxides of silicon, iron, and aluminium. The hardness and brittleness persist even when wet. centimoles/kg or (Cmol/kg): Unit used to express exchange capacity and exchangeable cations. Replaces me/100 g. 1 Cmol/kg soil = 1 me/100 g. centre-pivot irrigation: Automated sprinkler irrigation achieved by automatically rotating the sprinkler pipe or boom, supplying water to the sprinkler heads or nozzles, as a radius from the centre of the field to be irrigated. Water is delivered to the centre or pivot point of the system. The pipe is supported above the crop by towers at fixed spacing and propelled by pneumatic, mechanical, hydraulic, or electric power on wheels or skids in fixed circular paths at uniform angular speeds. Water is applied at a uniform rate by progressive increase of nozzle size from the pivot to the end of the line. The depth of water

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applied is determined by the rate of travel of the system. cereal: Seeds of flowering plants of the grass family (Graminaceae) cultivated for the food value of their grains, e.g., rice, wheat, sorghum, maize, oat, barley, rye, and millet. The word ‘ceres’ means the godess of grain. chaff: The glumes, lemmas, paleas and lighter plant tissue fragments released in threshing. chalk: It is a soft, pure, earthy, fine-textured, usually white to light gray or buff limestone of marine origin, consisting almost wholly (90-99%) of calcite, formed mainly by shallow-water accumulation of calcareous tests of floating microorganisms (chiefly foraminifers) and of comminuted remains of calcareous algae (such as cocoliths and rhabdoliths), set in a structureless matrix of very finely crystalline calcite. The rock is porous, somewhat friable, and only slightly coherent. channery soil material: Soil material that is, by volume, 15 to 35 percent thin, flat fragments of sandstone, shale, slate, limestone, or schist as much as 6 inches (15 centimetres) along the longest axis. A single piece is called a channer. Very channery soil material has 35 to 60 percent channers, and extremely channery soil material has more than 60 percent channers. characteristics curve or moisture release curve: Is the relationship (function) between soil moisture tension and the moisture content in the range from field capacity to wilting point. charcoal: A porous solid product containing 85-98% carbon and produced by heating carbonaceous materials such as cellulose, wood or peat at 500-600 degrees C in the absence of air. check dam: Small dam built across a gully or other small watercourse at suitable points to control water levels and regulate downstream discharges. check irrigation: Modification of a border strip with small earth ridges or checks constructed at intervals to retain water as the water flows down the strip. check row planting: The process of planting in which row to row and plant to plant distances are uniform and plants across the rows are also in line. check-basin irrigation: Check-basin method of irrigation is the most common method among surface methods of irrigation. In this method the field is

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chelated compounds (fertilizers)

divided into small plots surrounded by small bunds on all the four sides. Water from head channel is supplied to the filed channels one after the other. Each field channel supplies water to two rows of check basins and water is applied to one basin after another. This method is adopted when the field is quite large and is not easy to level the entire field. In such situations, the field is divided into small strips and each strip into several plots by putting bunds and these plots are called check basins. The advantage of this method is that the water can be applied uniformly and effectively. It is suitable for close growing crops like groundnut, wheat, fingermillet, pearlmillet, paragrass, etc. The disadvantages are more labour is required; more land is wasted under channels and bunds. Intercultivation is not possible due to bunds. chelated compounds (fertilizers): Fertilizer in which one or more trace elements are held by complex organic molecules (chelating agents) and are gradually released, thus prolonging the period of plant availability. Compounds consisting of a metal cation bound by an organic compound (chelate or ligand). Example: chelated fertilizers containing micronutrient cations (Zn-EDTA, Fe-EDTA, Fe-EDDHA etc). chelates: Organic chemicals with two or more functional groups that can bind with metals to form a ring structure. Soil organic matter can form chelate structures with some metals, especially transition metals, but, much metal ion binding in soil organic matter probably does not involve chelation. Artificial chelating compounds are sometimes added to soil to increases the soluble fraction of some metals. Examples are: EDTA (Ethylenediaminetetraacetic acid), HEDTA (Hydroxyethylethylenediaminetriacetic acid) and DTPA (Diethylenetriaminepentaacetic acid), etc. Some organic compounds obtained from nonsynthetic (natural) sources which are used for chelation of metal cations are lignosulphates, phenols and polyflavonoids obtained as organic by-products of wood pulp industry. chemical decomposition: A process where a chemical substance changes into simpler compounds or constituent elements. chemical element: A fundamental substance comprising one kind of atom; the simplest form of matter. chemical equation: A compact notation for describing a chemical change. The formulas of the reactants are

added together on the left hand side of the equation; the formulas of the products are added together on the right side. Coefficients are inserted before the formulas to ensure that the equation is balanced. The phase in which each substance is found is usually indicated in parentheses after each formula. For example, 2H2 (g) + O2 (g) = 2H2O (g) indicates that 2 moles of hydrogen gas combine with one mole of oxygen gas to produce two moles of steam. chemical fallow (eco-fallow): A special case of fallowing in which all vegetative growth is killed or prevented by use of chemicals; tillage for other purposes may or may not be used. chemical fallowing: Chemical fallowing is the use of herbicides instead of tillage to kill volunteer vegetation on the fallow fields. It leaves the ground under a dry vegetation mulch, which protects the soil against erosive agencies and paves the way to larger storage of rain in soil. chemical fixation: The process by which certain nutrient elements in a soil are converted from their available form to unavailable form. Examples are potassium, ammonium, and phosphorus fixation. chemical oxygen demand (COD): A measure of the oxygen-consuming capacity of inorganic and organic matter present in water or wastewater (e.g. sewage). The COD test, like the BOD test, is used to determine the degree of pollution in an effluent. The COD includes BOD. Also see biochemical oxygen demand (BOD). chemical potential: (i). The rate of change of Gibbs free energy, G, with respect to the number of moles of one component in a mixed chemical system at fixed temperature, pressure and number of moles of other components. (ii). The chemical potential of a component increases with increasing concentration or partial pressure. chemically precipitated phosphorus: Relatively insoluble phosphorus compounds resulting from reactions of phosphorus with soil constituents: e. g. calcium and magnesium phosphates which are precipitated above a pH of about 6.0 to 6.5 (if calcium and magnesium are present); and, iron and aluminium phosphates which are precipitated below a pH of about 5.8 to 6.1. chemigation: The practice of application of chemicals through irrigation water (Chemical + Irrigation). Similar to fertigation.

chlorine-critical level

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chemoautotroph: An organism that derives its energy from various chemicals and its carbon from CO2. Known also as chemoautotrophic organisms. Example: nitrifying bacteria.

chestnut soil: A zonal great soil group consisting of soils with a moderately thick, dark-brown A horizon over a lighter coloured horizon that is above a zone of calcium carbonate accumulation.

chemodenitrification: Chemical or non-microbial loss of nitrogen in gaseous form from the soil, in contrast to denitrification caused by bacteria.

chicory: Chicory (Cichorium intybus, and called succory by some) is a hardy plant that has a variety of uses but is best known for its association with coffee. When coffee has become unavailable or very costly, as during World War II, roasted chicory root has been used as a substitute or a blend, though there is no caffeine in chicory. Chicory also is said to offer health benefits and is used as a dietary supplement by some people. The young leaves can be used in salads, and the root can also be boiled and eaten like a vegetable (it is related to endive and radicchio). It is also an objectionable weed plant in berseem seed production.

chemoheterotroph: An organism that derives its energy from various chemicals and its carbon from organic molecules other than CO2 (e.g. glucose). Also known as chemoheterotrophic organisms. Example: Bacillus polymyxa, the phosphate solubilizing bacteria. chemolithotroph: An organism capable of using CO2 or carbonates as the sole source of carbon for cell biosynthesis, and deriving energy from the oxidation of reduced inorganic or organic compounds. Used synonymously with “chemolithoautotroph” and “chemotroph”. chemoorganotroph: An organism for which organic compounds serve as both energy and carbon sources for cell synthesis. Used synonymously with “heterotroph”. chemosphere: A vaguely defined region of the upper atmosphere in which photochemical reactions take place. It includes the top of the stratosphere, all of the mesosphere, and sometimes the lower part of the thermosphere. chemostat: A device for the continuous culture of microorganisms in which growth rate and population size are regulated by the concentration of a limiting nutrient in incoming medium. chemosterilant: A chemical that controls pests by preventing reproduction, thereby causing the population to collapse. This contrasts with chemicals that directly kill pests. chemotaxis: The oriented movement of a motile organism with reference to a chemical agent. May be positive (toward) or negative (away) with respect to the chemical gradient. chernozem: A zonal great soil group consisting of soils with a thick, nearly black or black, organic matter-rich A horizon high in exchangeable calcium, underlain by a lighter coloured transitional horizon above a zone of calcium carbonate accumulation; occurs in a cool subhumid climate under a vegetation of tail and midgrass prairie.

chilean nitrate of soda (Chile saltpetre): A product obtained by refining the crude nitrate deposits found in Chile and containing about 99% sodium nitrate which contains about 16% nitrogen. chipko movement: A local movement that began in India in the early 1980s and is opposed to deforestation. chisel: To break up soil using closely spaced gangs of narrow shank-mounted tools. It may be performed at other than the normal ploughing depth. Chiseling at depths >40 cm is usually termed subsoiling. chlorinated hydrocarbons: Hydrocarbons that contain chlorine. These include a class of persistent insecticides that accumulate in the aquatic food chain. Among them are DDT, aldrin, dieldrin, heptachlor, chlordane, lindane, endrin, Mirex, hexachloride, and toxaphene. chlorinated solvent: An organic solvent containing chlorine atoms that is often used as aerosol spray container, in highway paint, and dry cleaning fluids. chlorination: A water purification process in which chlorine is added to water for disinfection, for the control of present microorganisms. It is also used in the oxidation of compound impurities in water. chlorine (Cl): Its essentiality for plants was established by T.C. Broyer et al. in 1954. Absorbed by plants as Cl-. Usual concentration in plant dry matter 0.2-2%. chlorine-critical level: Concentration of chloride in soils or plants below which the soil/plant is

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chlorine-deficiency

considered deficient in Cl and a significant response to its application can be expected. The critical concentration depends on soil, crop, cultivar and yield potential. Critical concentration in the plant tissue can be between 2 and 20 ppm Cl but values of 70-700 ppm Cl also exist in the literature. chlorine-deficiency: Most soils contain sufficient levels of chloride for adequate plant nutrition. However, reported chloride deficiencies have been observed on sandy soils in high rainfall areas or those derived from low-chloride parent materials. Deficiency symptoms of chlorine are: chlorosis in younger leaves and overall wilting due to possible effect on water loss through transpiration. chlorine-fertilizers: Chlorine-containing compounds which can be used to provide Cl for crop nutrition. Example: potassium chloride KCl (47% Cl), NP/ NPK complexes in which KCl is an input, sodium chloride NaCl (60% Cl) and ammonium chloride (66% Cl). chlorine-functions: Because chloride is a mobile anion in plants, most of its functions relate to salt effects (stomatal opening) and electrical charge balance in physiological functions in plants. Chloride also indirectly affects plant growth by stomatal regulation of water loss. Chlorine is thought to be involved in the production of oxygen during photosynthesis, for raising cell osmotic pressure and in maintaining tissue hydration. The enzymes known to require Cl are á-amylase, ATPase and asparagine synthetase. The role of chloride in decreasing the incidence of various diseases in small grains is perhaps more important than its nutritional role from a practical viewpoint. chlorine-toxicity: Stage associated with adverse effect of excess chloride on a plant. This is reflected by burning of leaf tips or margins, bronzing, premature yellowing and leaf fall and impairment in the burning quality as in case of tobacco. chlorite: A group of layer silicate minerals of the 2:1 type that has the interlayer filled with a positively charged metal-hydroxide octahedral sheet. There are both trioctahedral (e.g., M = Fe(II), Mg2+, Mn2+, Ni2+) and dioctahedral (M= Al3+, Fe3+, Cr3+) varieties. chlorofluorocarbons (CFCs): Any of several gaseous compounds that are derivatives of methane, contain carbon chlorine and fluorine, and are used especially as aerosol propellants and refrigerants; suspected to

be a major cause of ozone depletion. The basic chemical formula for chlorofluorocarbons is CFx Clx. chlorophyll meter: The SPAD 502 model chlorophyll meter developed by the soil-plant analysis department (SPAD) section of Minolta Camera Company is light weight (in 275 g), portable, quick and reliable. With a leaf inserted, the meter displays a 3-digit SPAD value representing a relative measure of leaf greenness rather than the chlorophyll concentration. The logic behind using the chlorophyll meter as a diagnostic tool to determine the plants need for additional fertilizer N is based on the fact that leaf N concentrations are positively correlated with yield and that leaf N correlates with leaf greenness. The meter displays a 3-digit SPAD value proportional to the amount of chlorophyll present in the leaf by measuring the transmittance of the leaf in two wavelengths (600-700 nm and 400-500 nm). The meter is powered by two AA-size 1.5 volt batteries that provide more than 20,000 readings with an interval of several seconds between the measurements. It has capability for data recall of up to 30 values, individual data delete and averaging. A reference standard provided with the meter assures reliability. Currently, the meter costs approximately US $ 1,500. The chlorophyll meter has several advantages over other tissue testing methods. A reading that indicates adequate nitrogen (or critical value) is not affected by luxury consumption; a plant will only produce as much chlorophyll as it needs regardless of how much N is in the plant. It is not necessary to send samples to a laboratory for analysis, saving time and money. Producers can sample as often as they choose, and can easily repeat the procedure if they question the results. Using a chlorophyll meter to monitor leaf greenness throughout the growing season can signal the approach of a potential N deficiency early enough to correct it without reducing yields. Monitoring crop N status during the growing season accomplishes little unless it is possible to correct an N deficiency before it reduces yields. chlorosis: A nutrient stress condition in plants associated with loss of chlorophyll, resulting in loss of green colour accompanied by paleness and yellow colouration of the tissue. Example: iron chlorosis. chroma: The relative purity, strength, or saturation of a colour; directly related to the dominance of the determining wavelength of the light and inversely

clay related to grayness; one of the three variables of colour. chronosequence: A group of related soils that differ, one from the other, primarily as a result of differences in time as a soil-forming factor. chute spillway: The overall structure, which allows water to drop rapidly through an open channel without causing erosion. Usually constructed near the edge of dams. circuitous pattern: A ploughing pattern or technique where the operator first moves clockwise around the field, then counterclockwise toward the centre. It is commonly used in small rectangular fields. cirrocumulus cloud: Patchy white high altitude cloud composed of ice crystals. Found in an altitude range from 5,000 to 18,000 metres. cirrostratus clouds: High altitude sheet like clouds composed of ice crystals. These thin clouds often cover the entire sky. Found in an altitude range from 5,000 to 18,000 metres. cirrus clouds: High altitude clouds composed of ice crystals. The appearance of these clouds is white feather like patches, filaments or thin bands. Found in an altitude range from 5,000 to 18,000 metres. citrate-insoluble P: The P content in residue left after extracting citrate-soluble P, unavailable to plants. Examples: Rock Phosphate; Bone meal [Ca3(PO4)2]3CaF2. Water and citrate-soluble P is available to plants. citrate-soluble P: The fertilizer residue left after extracting water-soluble P with a neutral (pH 7.0) solution of 1N Ammonium citrate for a prescribed time (AOAC, 1960), and slurry is then filtered. The P content in the filtrate is then determined and expressed as % by weight of the fertilizer. The above fraction is called as citrate-soluble P. Examples: Dicalcium phosphate [CaHPO4]; Basic-slag (byproduct of steel Industry, useful for acidic soils); Calcium Metaphosphate[Ca(PO3)2]. class ‘A’ pan (USWB evaporimeter): It is a standard evaporimeter (120.7 cm in diameter and 25 cm deep) maintained in agrometerological observatories, which is helpful in generating data on evapo-transpiration, which in turn, can be used for scheduling of irrigation. classical biological control: The intentional introduction and permanent establishment of an exotic biological control agent for long-term pest control.

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clastic: Pertaining to rock or sediment composed mainly of fragments derived from preexisting rocks or minerals and moved from their place of origin. The term indicates sediment sources that are both within and outside the depositional basin. clay complex: A term used for the colloidal clay fraction of soil, which houses the cation exchange sites. Along with organic matter, the clay complex determines a soil’s cation exchange capacity (CEC). Plays a very important role in nutrient retention and release. clay films: Coatings of oriented clay on the surfaces of peds and mineral grains and lining pores. Also called clay skins, clay flows, illuviation cutans, or argillans. clay loam: Soil material that contains 27 to 40% clay and 20 to 45% sand. clay minerals: Clay minerals are the most important chemical weathering product of the soil. Clay minerals are important in soils because of the negative charge they contribute for cation exchange. Clay minerals are part of the larger class of silicate minerals: the phyllosilicates. Included in the phyllosilicate family are the larger true micas, which include the familiar minerals muscovite and biotite. Silicate Clay Minerals are called aluminosilicates and they have a definite crystalline structure. Clay minerals are very small in size (by definition are less than 0.002 mm in size) and only seen with the aid of electron microscope. Clay minerals are composed of two basic building blocks. (i). Silicon - Oxygen Tetrahedron (Si2O5)-2 (ii). Aluminium Octahedral (Gibsite Sheet) Al(OH)6-3. Tetrahedral sheets are composed of individual tetrahedrons, which share every three out of four oxygens. They are arranged in a hexagonal pattern with the basal oxygens linked and the apical oxygens pointing up/down. Octahedral sheets are composed of individual octahedrons that share edges composed of oxygen and hydroxyl anion groups with Al, Mg, Fe3+ and Fe2+ typically serving as the coordinating cation. These octahedrons too, are arranged in a hexagonal pattern and called a gibsite sheet. clay: (i). A soil separate consisting of particles