Madison, Wisconsin: Water Resources Center, University of Wisconsin–Madison
Nitrate (NO³) contamination of groundwater has been well documented. Nonpoint sources resulting from fertilizer use in agriculture are often to blame for much of this contamination. The research presented in this report was conducted to determine the rate at which nitrogen (N) moves through the root zone to the vadose zone of soils and the groundwater under a sandy soil along the Lower Wisconsin River Valley (LWRV). Rainfall was greater than normal during the 1990 growing season; several large storms caused deep percolation of water and NO³. The largest storm (7cm) occurred immediately following N fertilizer application, creating a worst-case scenario with respect to NO³ leaching. As a result of this storm, appreciable increases in NO³-N in soil-solution occurred as deep as 250 cm (8 ft) in the 12 days following N application. A six-ford increase in NO3 -N concentrations was found in groudwater samples collected adjacent to the research plots 2 months after nitrogen fertilization.