Water Quality and Crop Production Improvement Using a Wetland-Reservoir and Draining/Subsurface Irrigation System

In a wetland-reservoir system, tile drainage water and surface runoff water from agricultural fields are routed into a wetland reservoir, rather than into open-ended streams and drainage ditches. The collected water is then recycled back through a controlled tile drainage-subsurface irrigation system to provide subsurface irrigation during times of crop water deficit. The wetland reservoir provides wildlife habitat and serves as a sink to prevent off-site movement (loss) of water and sediments, and also provides a means for intercepting and recycling agricultural nutrients and chemicals via return irrigation. As a result, precipitation water is used more efficiently and the discharge of agricultural sediments and chemicals into off-site surface and ground water resources is substantially reduced. The controlled drainage/subirrigation system (CDS) reduced total nitrate loss by 41% compared to traditional tile drainage (DR). The CDS system also reduced losses of dissolved inorganic phosphorus, dissolved organic phosphorus and total dissolved phosphorus in tile drainage water by 18%, 47% and 36%, respectively, relative to the non-irrigated DR system. During the low rainfall growing seasons of 2001 and 2002, the CDS system increased corn grain yield by 91% (2001) and soybean yield by 49% (2002), relative to the DR system. Thus, the CDS system combined with a wetland-reservoir can be highly effective for improving crop yield and reducing non-point source pollution from agricultural fields.