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

Abstract

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.

Keywords:

• Algal‐available phosphorus
• broiler litter
• HAP corn
• reactive phosphorus
• runoff
• total phosphorus