Drainage water recycling (DWR), capturing and reusing subsurface drainage water for supplemental irrigation, offers the potential to increase climate resiliency and reduce nutrient losses of crop production. This study is evaluating DWR impacts on crop yield and water quality at three sites in Iowa. Additionally, a geospatial analysis was conducted to assess for DWR sites across four regions of Iowa. A DWR site near Story City has been operational since 2016. Supplemental irrigation was applied in five of six years, and DWR increased corn yields in all five years with an average increase of 2.2 Mg/ha (35 bu./ac.). A crop modeling exercise indicated that 6 inches of irrigation water availability would maximize the yield benefit. DWR reduced nitrogen loads, but results for phosphorus were mixed. Total nitrogen load reductions ranged from 63% to 90% in 2022. Total phosphorus loads were reduced by 66% at one site, whereas another site was a phosphorus exporter. The geospatial analysis identified 503 potential sites with up to 55,777 ha (137,829 ac.) suitable for DWR within the total 2,242,155 ha (5,540,365 ac.) of the four regions evaluated. These results will be used for landowner outreach to identify high priority pursuit areas for practice implementation. Well-sited DWR projects can provide production benefits to the farmer, drainage benefits to neighboring lands, and downstream water quality benefits. DWR has the potential to transform crop production on drained lands, creating cropping systems that are more resilient to climate risks and promoting long-term sustainability.
