Optimization of water-use efficiency in crop production systems by dynamic simulation of crop behavior under stochastic regimes

The objective of this study is to develop a systems simulation model for the management of irrigation water by maximizing water-use efficiency in a crop production system. A stochastic dynamic simulation model is proposed to simulate the relationships and interactions between a growing crop, the water reserves in its root zone, a seasonal stochastic weather pattern and the irrigation decision-making. The model is dynamic in that all four main components of the system change with time, and the system response is also a function of its past history. Irrigation management has been analyzed as an inventory system in which water in the root zone of the crop is its demand item, and in which management must decide 'when' and 'how much' to irrigate for optimal yields. Taking a limited irrigation water allocation at the beginning of the crop growing season as the system constraint, this study addresses itself to the problem of using this water optimally over an irrigation season by appropriate decisions regarding irrigation time and amount. Significant aspects of the modeling approach are: (i) crop yield and foliage development are directly related to the plant water deficit, (ii) the yield susceptibility of the crop to water deficit is a function of the growth stage, (iii) the irrigation scheduling is directly related to plant water deficit and yield susceptibility, (iv) the regulation of transpiration water losses by the leaf stomata is accounted for, and (v) relevant crop-and site-specific data are utilized.