Submitted to: Complete Book
Publication Type: Book / Chapter
Publication Acceptance Date: January 12, 2009
Publication Date: April 27, 2009
Citation: Ahuja, L.R., Reddy, V., Saseendran, S.A., Yu, Q. 2009. Responses of Crops to Limited Water: Understanding and Modeling Water Stress Effects on Plant Growth Processes. Complete Book. Madison, Wisconsin. American Society of Agronomy, Inc., Crop Soil Science Society of America, Inc., Soil Science Society of America, Inc. 436 p. Technical Abstract: The semi-arid regions of western U.S., India, China, and other parts of the world produce a major portion of the world’s food and fiber needs—from staple food grains of wheat, rice, and corn, to vegetables, fruits, nuts, wine, cotton, and forage crops for cattle and poultry. Most of this production in the semi-arid lands is achieved with irrigation. Over all agricultural land in the world, irrigation is practiced on about 20% of the area, but accounts for about 40% of the production. Many populous regions of the world such as south and east Asia are dependent on irrigation to meet food requirements. However, due to increase in population, urbanization, and environmental consciousness, the water demands for drinking, sanitation, urban irrigation, industry, and environmental uses are outbidding and reducing the water available for agriculture. Shrinkage of groundwater resources, such as the depletion of aquifers in India, China, and U.S., and the prolonged drought in the last few years have aggravated the situation. Greater frequency of more severe droughts predicted by some global climate change models are a cause for great concern. In addition, the global warming appears to be increasing the water requirements (evapo-transpiration demand) of plants. So, the questions for the western U.S. and all semi-arid regions of the world are: 1) how can the irrigated agriculture sustain productivity and meet the nation’s growing need for food and fiber with reduced water available for irrigation; and 2) what research knowledge and technologies are needed to accomplish this sustainability. The answers lie, along with other supporting measures, in simultaneously achieving: (1) the conservation of both rain and irrigation water in the field by managing to cut losses by runoff, deep percolation, and evaporation; (2) preserving the quality of groundwater and soil by preventing salinity development and nitrate and pesticide pollution; and (3) increasing the water use efficiency of crops by optimizing irrigation with respect to rainfall, critical growth stages, soil fertility, & weather conditions; optimize allocation of limited water among crops; optimal selection of crops by regions and selecting alternate crops in drought years. These goals will require a whole-system quantitative approach to guide management and achieve optimization of water application and crop performance, while protecting water quality and the environment. The computer models of agricultural systems are the essential technology needed for this purpose. The system modeling technology will also help conserve and make the most use of rainwater in rain-fed agricultural areas, including water-limited cropping or forage-livestock systems at field and farm levels. These areas comprise about 60% of the agriculture in the world. Prolonged drought in the last few years has especially aggravated the situation in these dry-land areas. The farmers and ranchers need simple tools to manage the systems during droughts. These tools can be derived from system models. Experience of the initiators of this volume has shown that all key current models of agricultural systems, although adequate for some purposes, need further improvement in the area of simulating the response of crops to limited water under various management and application options required for the above-noted applications (Ma et al., 2002). For this purpose, we hosted the 36th annual conference of the Biological Systems Simulation Group here in Fort Collins, CO, April 11-13, 2006, and organized a 1-day special session on “Recent advances in understanding and modeling of water stress (water deficit) effects on plant growth processes”. We invited and were fortunate in having the world’s experts in various aspects of this topic for this session (see Table of Contents). The speakers briefly provided the current state of science but emphasized more recent knowledge of the stress effects on processes that can be utilized to improve our models for crop responses to limited water applied at different growth stages. Purpose of this book then is to document this highly valuable knowledge so it can be used to improve the models. As much as possible and appropriate, a CD of all the submodels or models used in the Volume is provided with the Volume. The book will be indispensable for scientists, researchers, modelers, and students working in the crop production under limited water. The state of the science syntheses given in the papers will be highly useful for especially graduate level teaching. The new models or component codes will be valuable for graduate level teaching, research, and training of student in the use of models. All the papers in this Volume have been reviewed by two or more independent reviewers and by the editors for originality and quality, just as the journal papers. We assured that even the review papers made original contributions to synthesis of knowledge and/or development of new or improved concepts.