Modeling Water Quality Impacts in Delaware's Coastal Bays with AGNPS

The AGNPS model was used to model agricultural BMPs for the Delaware Inland Bays. Corn, soybeans and wheat were the crops used in the simulation. Conventional tillage with a winter cover crop along with minimum tillage and no-tillage with and without a winter coverage crop were simulated as BMPs. The model was calibrated with water quality and flow data from Stockely Branch, a 1359 ha watershed. The model was successful in predicting total runoff, but there was some variation in predicted and measured nitrogen and phosphorus loads for the nine storms used to calibrate the model. Nitrogen loads were more accurately predicted then phosphorus loads. For BMP simulations, winter cover crops had a large effect in reducing nitrogen and phosphorus loads regardless of tillage.