Crop Physiology: Applications for Genetic Improvement and Agronomy [1 ed.] 0123744318

Table of contents :
Cover Page ......Page 1
Copyright Page......Page 2
Preface......Page 3
Contributors......Page 5
Acknowledgements......Page 8
Introduction......Page 9
Agricultural Paradigms......Page 11
World trends in Population and Demand of Agricultural Products......Page 13
Productivity is the key but Inadequate for all Society’s Demands......Page 15
Part 2. Capture and efficiency in the use of resources: Quantitative frameworks......Page 19
Part 3. Crop physiology, breeding and agronomy......Page 20
References......Page 23
Farming Systems: Case Studies......Page 29
The nature of breeding by agronomy interactions and their relation to progress......Page 30
Some features of current Australian cropping......Page 33
General picture emerging from progress in wheat yields in Australia......Page 35
Genotype, seeding density and row spacing......Page 40
Selection for performance under low inputs......Page 41
Varieties tolerant to soil toxicities......Page 42
Fine-tuning crop duration to sowing options......Page 43
Dealing with weeds......Page 45
Dealing with diseases......Page 46
Crop Attributes for Reduced Tillage Systems......Page 47
Increased mechanical impedance......Page 48
Crop diversity and crop rotation......Page 49
Ley farming: crop–pasture rotation......Page 50
Adoption of Improved Varieties and Practices by Farmers......Page 51
Lessons and New Opportunities......Page 52
Acknowledgements......Page 56
References......Page 57
Introduction......Page 62
The Physical Environment......Page 63
Wheat......Page 65
Soybean after Maize......Page 68
Maize......Page 69
Risk Management......Page 70
Sunflower/Soybean Intercropping......Page 72
Canola/Soybean Double Crop......Page 73
References......Page 74
Improving Productivity to Face Water Scarcity in Irrigated Agriculture......Page 126
Introduction and Background......Page 127
Water use efficiency and water productivity......Page 129
Quantifying water use efficiency in irrigated agriculture......Page 130
A systematic approach for assessing the efficiency of water use......Page 131
Genetic improvement of WUE......Page 133
Optimising management to improve WUE: the role of evaporation......Page 134
Harvest index and water productivity in water-limited situations......Page 136
Yield formation and reproductive structures......Page 137
Carbon and nitrogen supply to grain: actual assimilation and reserves......Page 138
Field Irrigation Management and Efficient water use......Page 139
Optimising crop water supply under limited water......Page 140
References......Page 142
Introduction......Page 148
Estimation of RUE by Scaling up from leaf to Canopy......Page 149
Solar and PAR-based Radiation-use Efficiency......Page 150
Radiation-use Efficiency of main Crops......Page 151
Radiation-use Efficiency Response to Environmental, Plant and Management Factors......Page 154
Canopy size and architecture......Page 155
Temperature......Page 158
Air humidity......Page 159
Crop nutritional status......Page 162
Biomass partitioning between shoot and root......Page 163
Radiation-use Efficiency Response to Atmospheric Carbon Dioxide Concentration......Page 164
Improving Radiation Capture and use Efficiency: Agronomy and Breeding......Page 166
Concluding Remarks......Page 168
References......Page 169
Introduction......Page 174
Crop N Demand: Its Regulation at Plant and crop Levels......Page 175
Empirical approach......Page 176
Physiological principles......Page 178
Co-regulation of plant N uptake rate by both N soil availability and plant growth rate potential......Page 181
Diagnostic of plant N status in crops: nitrogen nutrition index......Page 183
Intra- and inter-specific interactions within plant stands......Page 185
Response of Plants and crops to N Deficiency......Page 186
Crop life cycle and plant N economy......Page 187
Radiation use efficiency and PAR interception......Page 188
Effect of N deficiency on canopy size and radiation interception......Page 190
Effect of N deficiency on leaf photosynthesis......Page 191
C and N allocation to roots......Page 193
C and N allocation to stems......Page 194
N distribution within the canopies......Page 195
Harvest index and components of grain yield......Page 196
N deficiency – water stress interactions......Page 197
N × P × S interactions......Page 198
Nitrogen use Efficiency......Page 199
N uptake efficiency......Page 201
Conclusions......Page 202
References......Page 204
Crop Physiology, Genetic Improvement, and Agronomy......Page 215
Ignoring Trade-offs Slows Progress......Page 216
Real, Imaginary and Complex Trade-offs......Page 220
Trade-offs as Constraints......Page 222
Trade-offs as Opportunities: Changed Conditions......Page 223
Trade-offs as Opportunities: Individual Versus Community......Page 224
Trade-offs as Opportunities: Conflicts Involving Microbial Mutualists......Page 227
Concluding Remarks......Page 229
References......Page 230
Introduction......Page 236
Modelling Biophysical Systems......Page 238
Development......Page 239
Radiation-limited growth......Page 241
Canopy development......Page 242
Reproductive growth......Page 243
Modelling Genotype–Environment–Management Systems......Page 244
Definition and consideration of the search space and adaptation landscapes......Page 245
From the top-down......Page 247
Genes, traits, phenotypes and adaptation......Page 248
Genotype–environment–management system......Page 249
Environmental classification......Page 250
Structure of simulated adaptation landscapes......Page 252
Exploring trajectories in GP space: what traits can improve adaptation?......Page 254
Opportunities to enhance molecular breeding......Page 256
How consistent are simulated trajectories with changes in traits due to genetic improvement for yield?......Page 257
Concluding Remarks......Page 259
References......Page 260
Color Plates ......Page 267
Introduction......Page 268
Contributions of biotechnology to crop physiology......Page 269
Contributions of crop Physiology to Plant Breeding and Biotechnology......Page 270
Interactions at the QTL or gene level......Page 271
References......Page 274
Crop Development......Page 278
Wheat......Page 279
Soybean......Page 283
Photoperiod......Page 285
Vernalisation......Page 287
Genes affecting development in wheat and related species......Page 288
Photoperiod response genes......Page 289
Photoperiod response genes......Page 290
Long-juvenile genes......Page 291
Crop development and adaptation......Page 292
Crop development and yield potential......Page 293
Concluding Remarks......Page 296
References......Page 297
Introduction......Page 310
Carbon Costs of Vigorous root Systems......Page 312
The role of vigorous root systems in capturing nitrogen......Page 316
The role of vigorous root systems in capturing water......Page 318
Root vigour and yield......Page 320
Challenges in Incorporating the Vigorous root Characteristic into Breeding......Page 321
References......Page 322
Introduction......Page 327
Modern Views in Plant Breeding......Page 329
Molecular-Assisted Genetic Improvement......Page 331
Identification of phenotype-associated markers......Page 332
MAS for improvement of qualitative traits......Page 334
MAS for improvement of quantitative traits......Page 336
Transgenic-Assisted Genetic Enhancement......Page 337
Transgenic applications......Page 338
Source:sink......Page 339
Resistance to biotic stress......Page 340
Qualitative and nutritional improvement......Page 341
Pre-breeding: a link between Genetic Resources and crop Improvement......Page 342
Breeding by Design......Page 343
References......Page 344
Rationale for Raising yield Potential......Page 355
Relationship between yield Potential and yield under Abiotic Stresses......Page 356
Changes in biomass and grain partitioning......Page 357
Changes in grain number associated with yield gains......Page 359
Changes in post-anthesis assimilate supply associated with yield gains......Page 360
Gains associated with the broadening of genetic background......Page 361
Hybrid breeding versus inbreeding......Page 363
Increasing fractional radiation interception......Page 364
Iincrease leaf photosynthetic rate......Page 365
Ddecrease respiration......Page 366
Root partitioning......Page 367
Structural and non-structural carbohydrate components of stem......Page 368
Ratio of grain to ear or panicle dry matter at anthesis......Page 369
Strategies to optimise potential grain size......Page 370
Use of spectral reflectance indices......Page 372
Use of stomatal aperture traits (SATs)......Page 373
Conclusions......Page 374
References......Page 375
Introduction......Page 386
Oil concentration......Page 387
Oil composition......Page 390
Protein concentration......Page 392
Protein composition......Page 394
Integration of quality Traits into crop Simulation Models......Page 396
Modelling grain protein concentration and composition in wheat......Page 397
Sunflower yield and oil composition......Page 399
Wheat yield and protein concentration......Page 401
Oil fatty acid composition......Page 404
Grain protein concentration......Page 405
Oil fatty acid composition......Page 406
Grain protein concentration......Page 408
Concluding Remarks......Page 409
References......Page 411
Introduction......Page 421
The Genetic basis of Resistance to Pathogens......Page 422
Polygenic resistance......Page 423
Colonisation of the plant host......Page 424
The structure of resistance genes......Page 425
The function of resistance genes......Page 427
Linking Genetics of Resistance with Agronomy......Page 428
Genetic control of wheat rust diseases......Page 429
Integrating agronomic practices with genetic resistance......Page 430
Negative effects of scaling up rust resistance breeding......Page 431
Gene deployment and minimum disease standards......Page 432
Crop composition......Page 433
Genetic effects of population size and patchiness......Page 434
Interplay of epidemiology and genetics in agricultural situations......Page 435
From Gene to Continent: Conclusions and future Prospects......Page 436
References......Page 437
Introduction......Page 446
Interference and competition......Page 447
Weed density......Page 449
Spatial distribution of weeds......Page 450
Timing of crop–weed interactions......Page 451
Competitive Ability of Crops......Page 453
Resource availability......Page 454
Resource use efficiency......Page 456
Water use efficiency......Page 457
Changes over time......Page 458
Variation in Competitive Ability Among Crop Species......Page 460
Traits Associated with Competitive Ability......Page 461
Shoot Traits......Page 462
Root traits......Page 465
Interactions between root and shoot growth......Page 466
Intraspecific competition......Page 467
Interspecific competition......Page 468
Resource allocation and dry matter partitioning......Page 469
Early vigour......Page 470
Flowering time and crop duration......Page 471
Heritability of competitive traits......Page 473
Genotype × environment interactions......Page 475
Molecular mapping of competitive traits......Page 476
Conclusions......Page 477
References......Page 478
Functional Sensing Approaches: Quantifying the Physiological Status of crops under water and Nitrogen Stresses......Page 486
Canopy temperature and related water stress indices......Page 487
Nitrogen stress indices......Page 491
Spatial prediction of crop maturity in peanut......Page 493
Simulation of crop development and maturity from thermal time......Page 494
Integrating the Spatial and Temporal Dimensions of on-farm Variability: The Role of Integrative Dynamic Systems Models......Page 497
The problem......Page 498
Integrating temporal and spatial dimensions of variability – a case study......Page 499
Conclusions and the way Forward......Page 502
References......Page 504
Colour Plates......Page 0
Realised trends......Page 511
Future projections......Page 512
Temperature......Page 514
Solar radiation......Page 516
Crop Models for Climate Change......Page 517
Modelling CO2 effect......Page 518
Modelling rainfall and rainfall variability effect......Page 519
Model validation......Page 520
Past trends......Page 521
Future scenarios......Page 523
Management......Page 525
Breeding......Page 528
Conclusions and Knowledge Gaps......Page 529
References......Page 531
Introduction......Page 544
C3 crop canopy net carbon exchange: a ‘gold standard’ reference for crop physiology?......Page 545
Root system structure and function......Page 546
Biomass partitioning......Page 548
High-temperature stress......Page 549
Low-temperature stress......Page 551
The Interface between crop Physiology and Modelling......Page 552
The Interface between crop Physiology and Breeding......Page 554
The Interface between crop Physiology and Agronomy......Page 556
Conclusions......Page 558
References......Page 560
A......Page 570
B......Page 571
C......Page 572
D......Page 573
E......Page 574
N......Page 575
P......Page 576
S......Page 577
W......Page 578
Y......Page 579

Citation preview

Cover Photo and Concept by Dr Pablo Calviño. Commercial-scale test of sunflower-soybean intercropping in the Pampas of Argentina. Originally a ”subsistence farming“ concept, here intercropping is a high-tech solution in one of the world’s more technologically advanced agricultural systems. Crop physiology and enabling agronomy are behind this innovative technology, as explained in Chapter 3, Section 5. Academic Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA 32 Jamestown Road, London NW 1 7BY, UK 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA Copyright © 2009, Elsevier Inc. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (44) (0) 1865 843830; fax (44) (0) 1865 853333; email: [email protected]. Alternatively visit the Science and Technology Books website at www.elsevierdirect.com/rights for further information. Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-12-374431-9

For information on all Academic Press publications visit our website at www.elsevierdirect.com Typeset by Macmillan Publishing Solutions (www.macmillansolutions.com) Printed and bound in the USA 09  10  11  10  9  8  7  6  5  4  3  2  1

Preface The problem of agriculture is that it has been too successful Elias Fereres

As a consequence of the success of post-World War II agriculture, particularly in western Europe, many in affluent societies have taken food for granted for decades. We lack historical perspective to conclude that the gap between the world demand and supply of food is widening or otherwise. Nonetheless, the recent debate on this gap and the role of research and development in agriculture is a positive signal. Nature (2008) has editorialised on this topic, highlighting the need to spend more on agricultural science to overcome food crises, whereas the point has also been made that not only the amount but also the allocation of research efforts is important (Struik et al., 2007). Current research efforts seem to be under divergent selection favouring either the very large or the very small. On the one hand, legitimate environmental concerns stimulate investments on global-scale issues. On the other hand, the internal dynamics of sciences at the molecular end of the scale, where progress is made at astonishing rates, has become a strong attractor of resources. Crop physiology belongs to the middle ground between these extremes. There are many hierarchical levels of biological organisation, from molecules to ecosystems. When we search for an understanding of biological phenomena, it is commonly found at levels below that of occurrence. Agro-ecosystem events are explained at the level of the crop, while molecular and cell biology will provide explanations to physiological responses. Besides, crop physiology provides a vital link between molecular biology and the agro-ecosystem. The peak of crop physiology appears to be in the past. Membership in the Crop Physiology and Metabolism Division of the Crop Science Society of America has declined concurrently with the initiation and rise of the Genomics, Molecular Genetics, and Biotechnology Division (Boote and Sinclair, 2006). This is a worldwide, rather than local, phenomenon, and a clear reflection of the shifts in research perspectives towards, in this case, the small. The objective of this book is to provide a contemporary appreciation of crop physiology as a mature scientific discipline. We want to show that much unfinished business lies in the domain of crop physiology, and that this intellectually challenging discipline is relevant to agriculture. Progress in agriculture, however, depends directly on progress in agronomy, plant breeding and their interaction. Hence crop physiology can contribute to agriculture only to the extent that it is meaningfully engaged with breeding and agronomy; this is the theme of this book. V.O. Sadras, Adelaide D.F. Calderni, Valdivia © 2009, 2009 Elsevier Inc.

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Preface

Boote, K.J. and Sinclair, T.R., 2006. Crop physiology: Significant discoveries and our changing perspective on research. Crop Sci. 46, 2270–2277. Nature, 2008. A research menu. Nature 453, 1–2. Struik, P.C., Cassman, K.G., Koorneef, M., 2007. A dialogue on interdisciplinary collaboration to bridge the gap between plant genomics and crop science. In: J.H.J. Spiertz, P.C. Struik and H.H. Van Laar (Eds.), Scale and Complexity in Plant Systems Research: Gene-Plant-Crop Relations. Springer, Dordrecht, The Netherlands, pp. 319–328.

Contributors Luis Aguirrezábal  INTA-Universidad de Mar del Plata and CONICET, Balcarce, Argentina� Vincent Allard  Institut National de la Recherche Agronomique (INRA), Clermont-Ferrand, France Fernando H. Andrade  INTA-Universidad de Mar del Plata and CONICET, Balcarce, Argentina� Maria Appendino  Universidad de Buenos Aires, Buenos Aires, Argentina Senthold Asseng  CSIRO Division of Plant Industry, Wembley, Australia Michael Ayliffe  CSIRO Division of Plant Industry, Canberra, Australia Robert Belford  Curtin University of Technology, Northam, Australia Grazia M. Borrelli  CRA – Centre for Cereal Research of Foggia, Foggia, Italy Jeremy J. Burdon  CSIRO Division of Plant Industry, Canberra, Australia Daniel Calderini  Universidad Austral de Chile, Valdivia, Chile Pablo Calviño  AACREA, El Tejar, Saladillo, Argentina Weixing Cao  Nanjing Agricultural University, Nanjiing, China Luigi Cattivelli  CRA – Centre for Cereal Research of Foggia, Foggia, Italy David Connor  University of Melbourne, Melbourne, Australia Mark Cooper  DuPont Agriculture & Nutrition, Johnston, IA, USA Pasquale De Vita  CRA – Centre for Cereal Research of Foggia, Foggia, Italy R. Ford Denison  University of Minnesota, Minnesota, MN, USA Zhanshan Dong  DuPont Agriculture & Nutrition, Johnston, IA, USA Elias Fereres  IAS-CSIC and University of Cordoba, Córdoba, Spain Ralph A. Fischer  CSIRO Division of Plant Industry, Canberra, Australia M. John Foulkes  University of Nottingham, Leicestershire, UK François Gastal  Institut National de la Recherche Agronomique (INRA), Lusignan, France Gurjeet S. Gill  University of Adelaide; School of Agriculture, Food & Wine, Waite Campus, Australia Victoria Gonzalez-Dugo  University of Córdoba, Córdoba, ������ Spain�

© 2009, 2009 Elsevier Inc.

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Contributors

David Guest  University of Sydney, Sydney, Australia Kaija Hakala  MTT Agrifood Research Finland, Jokioinen, Finland Antonio Hall  Universidad de Buenos Aires-IFEVA and CONICET, Buenos Aires, Argentina Graeme Hammer  University of Queensland, Brisbane, Australia Natalia Izquierdo  INTA-Universidad de Mar del Plata and CONICET, Balcarce, Argentina� Hannu Känkänen  MTT Agrifood Research Finland, Jokioinen, Finland Adriana C. Kantolic  Universidad de Buenos Aires, Buenos Aires, Argentina� Armen R. Kemanian  Texas Agricultural Experiment Station, Georgetown, TX, USA Gilles Lemaire  Institut National de la Recherche Agronomique (INRA), Lusignan, France Fulco Ludwig  Earth Systems Science & Climate Change Group, Wageningen University, Wageningen, The Netherlands Pierre Martre  Institut National de la Recherche Agronomique (INRA), Clermont-Ferrand, France Anna M. Mastrangelo  CRA – Centre for Cereal Research of Foggia, Foggia, Italy Glenn K. McDonald  University of Adelaide; School of Agriculture, Food & Wine, Waite Campus, Australia� Carlos Messina  DuPont Agriculture & Nutrition, Johnston, IA, USA Daniel Miralles  Universidad de Buenos Aires-IFEVA and CONICET, Buenos Aires, Argentina� Juan P. Monzon  AACREA, UNMdP, El Tejar, Saladillo, Argentina Jairo Palta  CSIRO Division of Plant Industry, Wembley, Australia Robert F. Park  University of Sydney, Sydney, Australia Pirjo Peltonen-Sainio  MTT Agrifood Research Finland, Jokioinen, Finland Gustavo Pereyra-Irujo  INTA-Universidad de Mar del Plata and CONICET, Balcarce, Argentina� Dean Podlich  DuPont Agriculture & Nutrition, Johnston, IA, USA Ana C. Pontaroli  INTA-Universidad de Mar del Plata, Balcarce, Argentina Ari Rajala  MTT Agrifood Research Finland, Jokioinen, Finland Matthew P. Reynolds  CIMMYT, DF, Mexico Andrew J. Robson  Queensland Department of Primary Industries and Fisheries, Queensland, Australia Daniel Rodriguez  Queensland Department of Primary Industries and Fisheries, Queensland, Australia Victor Sadras  South Australian Research & Development Institute, Adelaide, Australia Rodrigo G. Sala  INTA-Universidad de Mar del Plata, Balcarce, Argentina� Roxana Savin  University of Lleida, Lleida, Spain Ram C. Sharma  CIMMYT, Kathmandu, Nepal Gustavo A. Slafer  ICREA & University of Lleida, Lleida, Spain

Contributors

Claudio O. Stöckle  Washington State University, Pullman, WA, USA Roger Sylvester-Bradley  ADAS, Cambridge, UK Michelle Watt  CSIRO Division of Plant Industry, Canberra, Australia Weijian Zhang  Nanjing Agricultural University, Nanjiing, China

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Acknowledgements

Professor Antonio J. Hall contributed to maintain the focus of the book in difficult times, and provided insightful perspectives for many of the chapters in this book. Only his modesty prevented this book to count him as third editor. We thank the contribution of all the authors; their knowledge and time made this book possible. Reviewers who provided valuable input to one or more chapters include John Angus, Ken Boote, David Connor, Julio Dardanelli, Jenny Davidson, Tony Fischer, Antonio J. Hall, Anthony Hall, Peter Hayman, John Kirkegaard, Will Ratcliff and Huub Spiertz. We are grateful to our host organisations, the South Australian Research and Development Institute and Universidad Austral de Chile, for their support to this project. We thank Elsevier’s staff for supporting this project, especially Ms. Pat Gonzalez, Mr Mani Prabakaran and Dr. Andy Richford for their professional advise and support, and Ms. Christine Minihane for her work at early stages of the book. Throughout the book, key concepts developed by the authors are supported with material previously published in several journals. We thank the publishers who permitted to reproduce their material: American Society of Agronomy, Inc. (ASA), Crop Science Society of America, Inc. (CSSA) and Soil Science Society of America, Inc. (SSSA), American Society of Civil Engineers Publications (ASCE Publications), CSIRO Publishing, Édition Diffusion Presse Sciences (EDP Sciences), Elsevier, Food Product Press, Italian Society of Agronomy, Kluwer Academic Publisher, Limagrain, Oxford University Press, Springer, The Haworth Press, Weed Science Society of America and Wiley-Blackwell Publishers. Ana Ruben and Magda Lobnik helped with editorial checks and supported the editors with loving patience.

2009 Elsevier Inc. © 2009,

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CHAPTER 1

Sustainable Agriculture and Crop Physiology Victor Sadras, Daniel Calderini and David Connor … the herd of cattle was an animal who wanted to be many, or many animals that wanted to be one… Ricardo Güiraldes

1.  Introduction A view from space emphasises the areal dimension of agriculture (Loomis and Connor, 1996), which is threefold. First, the spreading of crops across the landscape allows for the effective capture of both aerial (sunlight, CO2) and soil (water, nutrients) resources that sustain crop growth (Loomis and Connor, 1996; Monteith, 1994). The linkage between spatial distribution of resources and plant growth requirements leads to predictable large-scale patterns of spatial distribution of vegetation (Miller et al., 2007), and competition for resources influences the structure and functioning of plant populations and communities (Benjamin and Park, 2007; Donald, 1981; Dybzinski and Tilman, 2007; Harper, 1977; Tilman, 1990). Second, smaller-scale space-dependent plant-to-plant interactions mediated by a wide array of signals allow plants to differentiate self and no-self, and respond to their neighbours before competition for resources arises (Aphalo and Ballaré, 1995; Aphalo and Rikala, 2006; Ballaré et al., 1990; Djakovic-Petrovic et al., 2007; Dudley and File, 2007; Karban, 2008; McConnaughay and Bazzaz, 1991). Third, there is an areal dimension in the definition of communities and ecosystems where the most significant aspects of agriculture are defined, including yield (Box 1) and resource conservation. A typical cropping field includes a thropic web of primary producers (crop species and weeds), and primary and secondary consumers, including herbivores, pathogens and predators; decomposers play a critical role in the geochemical cycles of major nutrients. Collectively, all these organisms constitute a community, which together with the physical and chemical attributes of the environment form an agro-ecosystem (Loomis and Connor, 1996). Crop physiology deals with the structure and functioning of crops, and is therefore closely related to plant sciences and ecology. The principles of crop physiology have been reviewed comprehensively, and are therefore out of the scope of this book. Readers interested in these principles are referred to a series of classical and more recent books (Charles-Edwards, 1982; Evans, 1975, 1993; Fageira et al., 2006; Gardener et al., 1985; Hay and Porter, 2006; Johnson, 1981; Loomis and Connor, 1996; Milthorpe and Moorby, 1979; Pessarakli, 1995; Smith and Hamel, 1999). In this chapter, we outline the paradigm of contemporary agriculture, and the challenge of sustainable production of bulk and quality food, fodder, fibre and energy during the next decades (Sections 2 and 3). We assess critically a range of agricultural aims and practices, including organic farming and production of land-based raw materials for biofuels; the environmental, economic or social flaws of these approaches are 2009 Elsevier Inc. © 2009,





CHAPTER 1:  Sustainable Agriculture and Crop Physiology

BOX 1  Crop yield: An evolving concept with multiple definitions Evolution of yield criteria For birds and mammals, natural selection favours the procurement of food at the lowest energy cost within the phylogenetic constraints of neural architecture (McLean, 2001). Before agriculture, our ancestors were therefore not unlike other animals, for which ‘yield’ was the ratio between the energy derived from food and the energy invested in obtaining food (Schülke et al., 2006). In the transition from foraging to farming, human populations were exposed to strong selective pressures to capture the full benefit of an energy-dense but initially detrimental food supply, including starchy cereals, roots and tubers, fatty meats, dairy products and alcoholic beverages (Patin and Quintana-Murci, 2008). Although the enzymatic machinery to metabolise these substances was already in place, the basal expression of such enzymes in our ancestors was inadequate to process the massive amounts of food brought about by farming. High levels of amylase in saliva or lactase in the small intestine probably conferred a strong selective advantage to early farmers (Patin and Quintana-Murci, 2008). Once the sowing of crops was established as a common practice, the definition of yield shifted from an energy ratio to the ratio between seed harvested and seed sown (Evans, 1993). This was particularly important in lowyielding seasons, when farmers had to make the hard decision of allocating seed for food and seed for the next sowing. An important consequence of this measure of yield was that selection possibly favoured highly competitive plant types, that is, abundant tillering, large inflorescences, small grain and weak seed dormancy (Evans, 1993). Only when availability of arable land came under pressure, mass of product per unit land area became a more important criterion. This shift in the definition of yield had a dramatic impact on selective pressures, shifting from the aggressive high-yielding plant (grains per grain) to the less competitive ‘communal plant’ able to produce more yield per unit area (Donald, 1981). Evans (1993) envisaged the next measure of yield whereby the time dimension is considered explicitly, for example, yield per hectare per year. This measure is particularly important when comparing productivity of systems where the degree of intensification is variable. Intensification of agriculture is a worldwide phenomenon (Caviglia et al., 2004; Farahani et al., 1998; Sadras and Roget, 2004; Shaver et al., 2003; Zhang et al., 2008). In this context, some observations of stabilisation or decline in yield (kg ha1)

(e.g. Cassman et al., 2003) could be a consequence of increasing cropping intensity. This is nicely illustrated by Egli (2008), who reported an inverse relationship between the rate of progress of the yield of soybean crops and the intensity of cropping measured as proportion of double crops in the system: the relative rate of yield improvement from 1972 to 2003 declined from 1.51% in counties with little or no double cropping to 0.66% in counties with 70% of land allocated to wheat-soybean double cropping. Paradoxically, the best environments supporting higher cropping intensity could therefore show the lower rate of improvement in the yield of individual crops. Explicitly measuring yield per unit area and time, as proposed by Evans, is therefore of increasing importance.

Yield of individual crops: Definitions Yields are in a continuum from crop failure to potential (Loomis and Connor, 1996), and several authors have proposed definitions to account for this range (Bingham, 1967; Evans and Fischer, 1999; Loomis and Amthor, 1999; Loomis and Connor, 1996; van Ittersum and Rabbinge, 1997). In this book, we favour the definitions of actual and attainable yield of Loomis and Connor (1996) and the definition of yield potential of Evans and Fischer (1999). Actual yield is the average yield of a district; it reflects the current state of soils and climate, average skills of the farmers, and their average use of technology. Actual yield also applies to the particular yield of a crop in a given paddock and season.

n

Attainable yield ‘corresponds to the best yield achieved through skilful use of the best available technology’.

n

Potential yield is ‘the maximum yield that could be reached by a crop in given environments’ as determined from physiological principles. As such, it is distinguished from yield potential, that is, the ‘yield of a cultivar when grown in environments to which it is adapted, with nutrients and water non-limiting and with pests, diseases, weeds, lodging and other stresses effectively controlled’. In this definition, environment emphasises solar radiation, temperature and day length (Evans and Fischer, 1999). Building on this definition, we propose that diffuse radiation and vapour pressure deficit need explicit consideration, alongside radiation and temperature (Rodriguez and Sadras, 2007). This is based on known phenomena,

n

(Continued)

2.  Agricultural Paradigms

BOX 1  Continued that is, higher fraction of diffuse radiation favours canopy photosynthesis (Roderick and Farquhar, 2003; Sinclair and Shiraiwa, 1993; Sinclair et al., 1992), and high vapour pressure deficit restricts growth of well-watered plants (Bunce, 2006; Gollan et al., 1985; Monteith, 1993; Sadras et al., 1993).

A ranking of yields is expected: Actual yield≤attainable yield