Mechanical Aeration to Reduce P Export from Manured Grasslands

Abstract

The poultry industry is an important component of agricultural production in the Southern Piedmont of Georgia. Associated manures are typically surface-applied to pastures as a fertilizer for forages. However, this surface application of manures allows phosphorus (P) to accumulate at the soil surface and runoff to become contaminated with P and to transport it to surface waters. As such, a study was conducted to examine the conservation potential of mechanical aeration of grasslands. Mechanical aeration has potential to reduce P transport by partially incorporating applied manures, allowing for more P adsorption by the soil, increasing infiltration by breaking the soil surface, and by slowing runoff flow by increasing the roughness of the landscape. We examined the effects of four aeration treatments (aeration with cores, “no-till” disk aeration perpendicular to the slope, aeration with spikes, and no aeration treatment) on the export of dissolved reactive P (DRP) in surface runoff from grasslands with two nutrient treatments (broiler litter and a control of no manure). Plots (0.75 x 2 m) were established on a Cecil soil series with mixed tall fescue/bermudagrass vegetation on 8 to 12% slopes. Plots were then aerated and manures applied at a rate of 30 kg P ha-1, prior to simulated rainfall at a rate of 75 mm h-1. While aeration had minimal impact on volume of runoff, core aeration decreased DRP loads (P < 0.05) from applied broiler litter by 61%. Given that Cecil soil is common in pastures receiving broiler litter in the Southern Piedmont, these results suggest that core aeration could have a widespread impact on water quality in the Southern Piedmont region.