Technical Abstract: The results show the value of the models to guide soil water management for plant production in complex agricultural systems. At the dawn of the 21 Century, computers are playing a central role in managing industries, businesses, and many other aspects of life. Their use in managing water and other natural resources and environmental quality is on the increase. It is time that computer models of agricultural systems be integrated with all field research, so that the models continually capture new knowledge as this becomes available. The models should then be used to guide agricultural management under varying climatic and weather conditions.