Deficit Irrigation Management for Multiple Fields and Years in the Great Plains

Scarcity of irrigation water supplies is leading to the need to consider deficit irrigation that is the intentional under-irrigation of crops resulting in evapotranspiration and yield reduction. We present analytical tools that can be used to assist irrigators and water managers in assessing the water balance and economic consequences of deficit irrigation alternatives. We combine a water balance model of an irrigated field with crop production functions and nonlinear optimization to identify optimal cropping choices and annual irrigation water allotments to crops. The methodology has been developed for planning for deficit irrigation management for conditions ranging from one field for a single year to allocation programs that focus on farms with multiple fields and multiannual water supply constraints. Example applications are presented to illustrate the methodology for typical conditions in the Central Great Plains of the United States.