Runoff Quality Impacts of Swine Manure Applied to Fescue Plots

Runoff concentrations of animal manure constituents are much higher for the first runoff-producing storm after land application than for subsequent storms. These concentrations are also inversely related to the interval between application and first runoff-producing storm. In terms of runoff quality, the worst situation is generally when the first runoff-producing storm occurs soon after application. This study was conducted to determine how potential first-storm runoff quality from fescue grass plots is affected by animal manure application rate and simulated rainfall intensity. Swine manure slurry was used in a factorial experimental design with three levels [0, 217, and 435 kg nitrogen (N)ha–1] of slurry application rate and two levels (5 and 10 cm h–1) of simulated rainfall intensity. The slurry was applied during moist soil conditions. Simulated rainfall was initiated 24 h following application. Runoff amounts and concentrations of slurry constituents (total Kjeldahl N, ammonia N, nitrate N, total phosphorus, dissolved reactive phosphorus, chemical oxygen demand, total suspended solids, and electrical conductivity) were determined. Analyses of variance were performed to assess the influences of the variables on both concentrations and event mass losses of the slurry constituents. Both runoff concentrations and event mass losses of all slurry constituents except nitrate N increased approximately linearly with application rate. Runoff concentrations of all slurry constituents except nitrate N decreased with increasing rainfall intensity, but event mass losses were unaffected.