Nitrogen Fertilizer, Cropping Systems, and Iowa Groundwater

Summary presentation of research conducted over a 5 year period to determine which cropping systems best reduce nitrate leaching. Initial data was collected on nitrate concentration from individual wells in the Sioux Center, Iowa area which led to connections with the Iowa Department of Natural Resources Source Water Protection Program. A community group was then formed comprised of city representatives, Dordt College faculty, local farmers, Source Water Protection Program staff, and others. The group applied for and received a Leopold Center for Sustainable Agriculture grant to fund field experiments to identify cropping systems that retain nitrate and are workable for producers. Five different cropping systems were tested over a five year period. These included continuous corn, continuous grass hay, oat/alfalfa/corn, oat/red clover/corn, and soybean/winter wheat/corn. Results of residual nitrate nitrogen levels for each of the crop rotations is presented along with preliminary economic summaries