Evaluating Drainage Water Recycling Benefits for Crop Production in Iowa

Drainage water recycling, storing subsurface drainage water for reuse as irrigation water, is a practice that is gaining interest to meet both production and environmental goals. There is limited research on the feasibility of this practice in Iowa and the rest of the U.S. Corn Belt. The objectives of this study were to quantify net irrigation requirements at multiple locations in Iowa, the potential supply of subsurface drainage water that could be stored for reuse, and the frequency that stored drainage water would be adequate to meet crop water demands. The growing season net irrigation requirement ranged from 114 mm to 269 mm for maize and 103 mm to 259 mm for soybean. The mean annual subsurface drainage depth was 226 mm. In 50% of years that irrigation was required, subsurface drainage water was adequate to fully meet crop water demands. These results are the first step towards understanding the feasibility and design requirements of drainage water recycling systems in Iowa.