Solids Transport and Erodibility of Poultry Litter Surface-applied to Fescue

Abstract

Poultry (Gallus gallus domesticus) litter is land-applied to make beneficial use of litter nutrients for plant growth. Runoff can transport litter particles off application sites and thus diminish the quality of downstream waters. This study assessed how solids (sediment and litter particles) yield and erodibility for fescue (Festuca arundinacea Schreb.) pasture are influenced by poultry litter application. The experimental variables were poultry litter application rate (0, 5.9, 11.8, and 23.5 Mg/ha), simulated rainfall intensity (50 and 100 mm/h), interval between litter application and simulated rainfall (1, 4, 7, and 14 days), and number of simulated rainfall events (four eventsone each at 7, 14, 36, and 68 days following litter application). Solids yields were determined from composite runoff samples. Erodibility values were computed from the Modified Universal Soil Loss Equation. Solids yield increased with increasing rainfall intensity and litter application rate. Erodibility increased linearly (r2 = 0.98) with litter application rate, but was unaffected by rainfall intensity. Neither solids yield nor erodibility was influenced by interval between litter application and first post-application rainfall. The number of rainfall events affected both solids yield and erodibility of litter-treated plots, but both approached levels observed for untreated plots by the third rainfall. The results indicate that models estimating erosion from fescue pasture treated with poultry litter should incorporate increased erodibility values to account for the presence of the litter. The adjustment, however, should be decreased with successive post-application rainfall events.