Phosphorus Losses in Runoff after Application of Litter from Broilers Fed High-Available Phosphorus Corn Feed

Recent efforts to reduce phosphorus (P) content of corn grain fed to poultry have led to the development of low-phytic-acid corn. Research is needed to evaluate the environmental impact of the application to cropland of manure from animals fed low-phytic-acid corn. The purpose of this research was to determine P losses in runoff from a bare Piedmont soil (cecil clay loam; clayey, kaolinitic, thermic, Typic Kanhapludult) in the southeastern United States receiving surface applications of broiler litter from birds fed a low-phytic-acid corn (HAP broiler litter). The HAP litter was applied at rates of 0, 8, 16, 33, 49, 66, and 82 kg P ha–1. Simulated rainfall was applied at a rate of 7.6 cm hr–1 on the same day the litter sources were applied to the plots. Runoff volumes were measured, and samples were collected at 5-min intervals for 30 min and analyzed for reactive P (RP), algal-available P (AAP), and total P (TP). Flow-weighted concentrations and mass losses of P increased linearly with litter application rate (r2 values = 0.99). Flow-weighted concentrations of RP in runoff increased from 2.2 to 15.4 mg RP L–1, and mass loss of TP in runoff ranged from 1.3 to 7.3 kg P ha–1 over all application rates based on linear regression. Runoff volume losses were 47% greater after litter applications compare to the 0 application rate treatment. Reduced infiltration resulting from litter particles blocking pores in the soil surface is likely the reason for the increased runoff volumes. Tarkalson & Mikkelsen in Comm. Soil SCi. & Plant anal. 38 (2007) 1806