Optimal Seasonal Irrigation Application Analysis

The concept of an optimal seasonal depth of infiltrated water for an irrigated crop is developed for the case when the yield is a quadratic function of the depth of water infiltrated, and the water distribution function is known. The cost of drainage is taken into consideration for those situations when the infiltrated depth is large enough to cause reductions in yield or large enough to warrant installation of a drainage system because of water logging or drainage problems elsewhere. In addition, the cost of leached nutrients or penalties or both for excess deep percolation are considered. An example is used to show how to determine the optimal infiltrated depth when the yield function and water distribution function are known. It is also shown how one can determine how much additional capital can be spent to improve an irrigation system's uniformity in order to increase the profit.