Using the NLEAP Model to Quantify the Amount and Depth of Leached Nitrogen.

The Sassafras River is listed on Maryland's 303 (d) list of impaired waters for having excessive levels of nutrients, sediment, and toxins. The river’s watershed, which is located in Cecil and Kent County Maryland, and New Castle County Delaware, is comprised of 57% agricultural land. The objective of this research was to use the Nitrate Leaching and Economic Analysis Package (NLEAP) model to quantify the amount and depth of leached nitrogen from agricultural fields in the Sassafras River watershed and to determine the effects that best management practices (BMPs) would have on nitrogen behavior. Inputs for the model include soil data collected from the National Resources Conservation Service (NRCS) Soil Data Mart, climate data from the NRCS-USDA National Weather and Climate Center, and crop data and management scenarios from area agriculturalists. Three scenarios were simulated over a 30-year time period with a three year crop rotation of corn, soybeans and wheat. The three scenarios simulated were no BMPs, conservation tillage, and fertilizer management. Simulation results indicated there were “hot spots” in individual fields where nitrogen leached below the root zone.  The NLEAP model was effective in identifying problem areas and in assessing the effectiveness of best management practices in reducing leached nitrogen.  This project was supported by Delaware EPSCoR, through National Science Foundation Grant EPS-0447610 and Wesley College.