Vegetative Cover Crops as a Nitrate Reduction Strategy for Tile Drainage

University of Minnesota/Jeff Vetsch

Nitrogen (N) is an essential input for profitable corn production. Previous research (Randall and Mulla, 2001, Dinnes et al., 2002) has shown subsurface tile drainage systems deliver nitrate-N to surface waters and thereby degrade water quality. Row crop agriculture in the Midwest is under scrutiny to reduce NO3 concentrations and loads in tile drainage. The use of cover crops and applying appropriate rates of N for corn are potential management strategies to reduce NO3 losses in tile drainage water (Dinnes et al., 2002). The species of cover crop, establishment date and termination date could greatly affect their potential to sequester N. Cereal rye is effective at scavenging N when it’s established early and not terminated until spring. Generally, Minnesota farmers who use cover crops either use cereal rye in a no-till system or seed a blend of annuals like oat, annual rye, clover and radish. These annuals are terminated by cold temperatures and/or tillage. The potential of fall/ winter terminated covers to scavenge N in a cornsoybean rotation in Minnesota is not well known.

The goal of this study is to quantify the effects and interactions of cover crop management and N rate on tile water flow, NO3-N concentration and loss in tile drainage water, corn and soybean production, N uptake and nitrogen use efficiency (NUE).