USE OF THE EPIC MODEL TO PREDICT RUNOFF TRANSPORT OF SURFACE-APPLIED INORGANIC FERTILIZER AND POULTRY MANURE CONSTITUENTS

The Erosion Productivity Impact Calculator (EPIC) model was applied to four fields established in ''tall'' fescue (Festuca arundinacea Schreb.) in northwestern Arkansas to predict runoff and transport of nitrogen, phosphorus, and sediment. Fertilizer form varied among the fields with two receiving inorganic fertilizer, one receiving poultry (Gallus gallus domesticus) litter, and one receiving poultry manure. Soil and grazing parameters also differed among fields. Runoff and nutrient/sediment transport observed over 20 months were compared to EPIC predictions generated without calibration. Significant correlation between event predictions and observations were found in half the cases. There was significant correlation between observed and predicted calendar year total transport for all outputs except nitrate-nitrogen. The findings indicate that EPIC can accurately reflect runoff quality trends when executed without calibration for pasture fields in northwestern Arkansas.