Current Water Deficit Stress Simulations in Selected Agricultural System Simulation Models

Authors: ANAPALLI, SASEENDRAN - COLORADO STATE UNIVERSITY; Ahuja, Lajpat; Ma, Liwang; Timlin, Dennis; STOCKLE, CLAUDIO - WASHINGTON STATE UNIV.; BOOTE, KENNETH - FLORIDA STATE UNIVERSITY; HOOGENBOOM, G - UNIVERSITY OF GEORGIA

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/8/2008
Publication Date: 12/1/2008
Citation: Anapalli, S.S., Ahuja, L.R., Ma, L., Timlin, D.J., Stockle, C.O., Boote, K.J., Hoogenboom, G. 2008. Current Water Deficit Stress Simulations in Selected Agricultural System Simulation Models. In: Ahuja, L.R., Reddy, V.R., Saseendran, S.A., Yu, Q., editors. Response of Crops to Limited Water: Understanding and Modeling Water Stress Effects on Plant Growth Processes. Madison, WI, American Society of Agronomy, Crop Science Society of America, Soil Science Society of America. p. 1-38.

Interpretive Summary: Water is fundamental for the normal physiological activities and membrane transport processes in plants, and as such is the most limiting factor in agriculture. Water deficit stress (hereafter referred to as ‘water stress’) refers to a condition in which plant cells and tissues are less than full turgor due to transpiration demand in excess of root water uptake, adversely affecting the growth and development processes and thus potentially limiting productivity. Increasing demand for agricultural products for food, fodder and fuel with increasing human population calls for more water allocation in the agricultural sector in the future. In this context, there is an increasing challenge for scientists to develop innovative soil-water-nutrient-crop management practices that are more water use efficient and sustainable. System models, which adequately simulate plant water stress effects, are valuable tools for developing management practices with improved water use efficiency in agriculture. A critical review of literature shows that the water deficit stress modulates: (1) phasic plant developmental rates, (2) leaf initiation and expansion growth, (3) photosynthesis, (4) carbon allocation and partitioning, and (5) root length and density in soil layers. In this paper, we present reviews of current simulations of plant water stress and its integration with crop growth and development processes in the APSIM, CropSyst, DSSAT (CERES and CROPGRO crop modules), GLYCIM and RZWQM models. In general, these models use the ratio of actual to potential transpiration or evapotranspiration to represent water stress. Potential evapotranspiration in general is computed using Penman-Monteith or Priestly-Taylor equations treating plant canopy as a big-leaf. In plants, the processes of carbon assimilation, transpiration, energy balance, and stomatal behavior are coupled. In the above models, there are no explicit simulations of leaf energy balance and leaf temperature, and stomatal conductance in quantifying transpiration and photosynthesis. For improved simulations of crop growth and development under water deficit conditions, accurate simulations of these coupled processes governing water movement through the soil-plant-atmosphere continuum is essential. Results of performance evaluations of the above models in specific water deficit experiments substantiated their potential in developing cost-effective and scientifically sound decision support tools in agricultural water management.

Technical Abstract: System models, which adequately simulate plant water stress effects, are valuable tools for developing management practices with improved water use efficiency in agriculture. Plants experience water stress when its supply in the soil fails to meet the demand. Although it is easy to define the concept, accurate quantification and representation of water stress in crop models have been a challenge in system modeling. A critical review of literature shows that the water deficit stress modulates: (1) phasic plant developmental rates, (2) leaf initiation and expansion growth, (3) photosynthesis, (4) carbon allocation and partitioning, and (5) root length and density in soil layers. In this paper, we present reviews of current simulations of plant water stress and its integration with crop growth and development processes in the APSIM, CropSyst, DSSAT (CERES and CROPGRO crop modules), GLYCIM and RZWQM models. In general, these models use the ratio of actual to potential transpiration or evapotranspiration to represent water stress. Potential evapotranspiration in general is computed using Penman-Monteith or Priestly-Taylor equations treating plant canopy as a big-leaf. In plants, the processes of carbon assimilation, transpiration, energy balance, and stomatal behavior are coupled. In the above models, there are no explicit simulations of leaf energy balance and leaf temperature, and stomatal conductance in quantifying transpiration and photosynthesis. For improved simulations of crop growth and development under water deficit conditions, accurate simulations of these coupled processes governing water movement through the soil-plant-atmosphere continuum is essential. In this article, we also reviewed and presented examples of models (those not included in the list of five models listed above) that address these coupled processes. Results of performance evaluations of the above models in specific water deficit experiments substantiated their potential in developing cost-effective and scientifically sound decision support tools in agricultural water management.