Runoff and losses of nutrients and herbicides under long-term conservation practices (no-till and crop rotation) in the U.S. Midwest: A variable intensity simulated rainfall approach

The U.S. Farm Bill includes conservation practices that benefit both the environment and the farmer. The USDA Conservation Effects Assessment Project (CEAP) is a multi-agency effort to assess the efficiency of conservation practices to minimize non-point source pollution. This is follow-up study of a 28-year experiment design to assess the influence of the conservation practices of no-till and crop rotation systems (corn [Zea mays]-soybean [Glycine max]), compared to chisel tillage and monocropping systems (continuous corn) on soil health and water quality. In this study, changes on soil C and N, soil water content, runoff, and losses of ammonium-N, nitrate-N, soluble reactive P (SRP), atrazine, metolachlor, and glyphosate were compared to determine the influence of no-till and corn-soybean rotation systems, relative to chisel tillage and continuous corn, on plots planted with corn using variable intensity rainfall simulations. The long-term no-till systems had a positive impact on soil C and N, soil water, runoff, and losses of ammonium-N and nitrate-N; however, no effect was observed on losses of SRP, atrazine, metolachlor, and glyphosate. The corn-soybean rotation negatively influenced, compared to the continuous corn, soil C and N, soil water content, and increased runoff and the losses of all nutrients and herbicides measured in this study. These results suggest that additional conservation practices, in conjunction with no-till and corn-soybean rotations are needed to reduce surface losses of nutrients and pesticides while improving soil health.