APPLICATION OF WEPP AND AGNPS TO A CATTLE GRAZING PASTURE WITH POULTRY LITTER APPLICATION AS A FERTILIZER

Water quality impairment in many streams and water bodies in the United States is primarily the result of non-point source pollution from agricultural watersheds. Water quality computer simulation models can assess the impact of cattle grazing pasture management practices on water quality. This study applied the single-event mode of the Agricultural Non-Point Source (AGNPS) and the Water Erosion Prediction Project (WEPP) models to simulate surface runoff and sediment yields from a grazed watershed (2.71 ha) in north Alabama. The models were used to evaluate three pasture vegetation types (Bermuda grass, fescue, and ryegrass) to recommend the best pasture vegetation type used in this study. Runoff samples collected from eleven storm events from January 1999 to September, 2003 were analyzed and compared with the antecedent moisture condition for AGNPS and initial saturation level for WEPP based model prediction. The AGNPS and WEPP models reasonably predicted surface runoff and sediment yields in this study.