NUTRIENT RUNOFF FROM PASTURE AFTER INCORPORATION OF POULTRY LITTER ORINORGANIC FERTILIZER

Land-applied poultry litter can elevate N, P, and C concentrations in surface water runoff. This study tested the hypothesis that incorporat ion of surface-applied poultry litter and inorganic fertilizer by rota ry tillage would improve runoff quality from tall fescue (Festuca arun dinacea Schreber) pasture. Captina silt loam (fine-silty, siliceous, m esic Typic Fragiudult) plots with 5% slopes and fescue cover received 4.5 Mg litter ha-1 or fertilizer equivalent to 218 kg N ha-1 and 87 kg P ha-1. Litter and fertilizer were surface applied or incorporated 2 to 3 cm deep by rotary tillage. Simulated rainfall was applied 7 d lat er at 50 nun h-1 to produce continuous runoff for 0.5 h. Runoff concen trations and mass losses of measured constituents were not significant ly different (alpha = 0.05) between surface-applied and incorporated t reatments. Runoff concentrations of total Kjeldahl N (TKN), NH3-N, NO3 -N, total P (TP), PO4-P, chemical oxygen demand (COD), and total suspe nded solids (TSS) averaged 32.5, 12.4, 1.1, 15.4, 10.4, 427.8, and 86. 8 mg L-1 for litter treatments, and 37.5, 39.0, 2.6, 26.2, 26.1, 87.8, and 20.6 mg L-1 for fertilizer treatments. Mass losses of TKN, NH3-N, NO3-N, TP, PO4-P, COD, and TSS averaged 2.8, 1.0, 0.1, 1.3, 0.9, 32.3 , and 6.7 kg ha-1 for litter and 2.9, 3.4, 0.2, 2.0, 2.0, 12.7, and 2. 1 kg ha-1 for fertilizer treatments. Runoff mass losses of TKN and TP were not significantly different between litter and fertilizer treatme nts. Averaged across all treatments and replications, mass losses of T KN and TP were 2.8 and 1.7 kg ha-1, representing 1.3% of applied N and 1.9% of applied P.