Effect of direct incorporation of poultry litter on phosphorus leaching from coastal plain soils

Management of poultry litter on the Delmarva Peninsula is critical to reducing phosphorus losses to the Chesapeake Bay. New poultry litter incorporation technologies have shown promise at reducing phosphorus losses, but their effectiveness has not been tested in this environmentally sensitive region. This study evaluates subsurface leaching losses of three litter application methods, including surface broadcast, surface broadcast with disking, and subsurface litter incorporation with a novel litter incorporator developed by the USDA Agricultural Research Service. Cube-shaped soil lysimeters (61 × 61 × 61 cm [24 × 24 × 24 in]) were extracted from high phosphorus (P) (Mehlich-3 P is greater than 500 mg kg^-1) agricultural soils on the University of Maryland Eastern Shore Research Farm near Princess Anne, Maryland, and were subjected to two rainfall simulation events that were separated by 11 semiweekly soaking-type irrigation events. The average cumulative total phosphorus loss was highest for the subsurface litter incorporation method (0.48 kg ha^-1 [0.43 lb ac^-1]) and was lowest for the no litter control (0.19 kg ha^-1 [0.17 lb ac ^-1]). Particulate P loss among manure treatments ranged from 58% to 64% of total P loss. Total phosphorus losses were strongly correlated to total phosphorus concentration in the leachate (coefficient of determination [r ²] ≥ 0.84), indicating availability of P in applied litter to be the primary control of P in leachate. Soil properties also impacted P leaching losses, with the soils possessing a higher sand content and having a shallower depth to the sandy subsoil, yielding higher cumulative total P losses (0.64 kg ha^-1 [0.57 lb ac^-1]). Although the subsurface litter incorporator increased total P leaching losses, a concern on the Delmarva Peninsula, opportunity exists to modify the subsurface incorporator design using zone tillage, potentially reducing the leaching losses.