title: Field-scale evaluation of phosphorus leaching in acid sandy soils receiving swine waste.
abstract: Accurate descriptions of P leaching are important because excess P applied to soils can enter surface water via leaching and subsurface transport, thereby negatively impacting water quality. The objectives of this study were to monitor P leaching in soils with a long-term history of waste application, relate soil solution P concentrations to soil P status, and quantify P leaching losses. Soil solution was monitored for 20 mo with samplers installed at 45-, 90-, and 135-cm depths in two pits (1 x 3 x 1.5 m) in Autryville (loamy, siliceous, thermic Arenic Paleudults) and Blanton (loamy, siliceous, semiactive, thermic Grossarenic Paleudults) soils located in a grazed pasture in Sampson County, NC, which had received swine waste for >20 yr. Maximum soil solution P concentrations at 45 cm exceeded 18 mg L(-1) in both soils. Soil solution P concentrations at 90 cm in the Blanton soil were similar to that at 45 cm indicating low P sorption. Soil solution P concentrations at 90 cm in the Autryville soil averaged 0.05 mg L(-1) compared to 10 mg L(-1) at 45 cm. A split-line model related soil solution P concentration to the degree of phosphorus saturation (DPS), identifying a change point at 45% DPS. Phosphorus movement past 45 cm equaled or exceeded surplus P additions for both soils. Long-term waste applications resulted in DPS > 90%, high soil solution P concentrations, and substantial vertical P movement. Phosphorus leaching should be considered when assessing long-term risk of P loss from waste-amended soils.
authors.affiliation: USDA-ARS Northwest Irrigation and Soils Research Laboratory, Kimberly, ID 83341-5076, USA. nnelson@nwisrl.ars.usda.gov
authors.forename: Nathan O
authors.initials: NO
authors.lastname: Nelson
authors.forename: John E
authors.initials: JE
authors.lastname: Parsons
authors.forename: Robert L
authors.initials: RL
authors.lastname: Mikkelsen
mesh_terms: D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D008372:Manure; D010758:Phosphorus / Q000378:metabolism*; D012987:Soil; D012989:Soil Pollutants / Q000378:metabolism; D013552:Swine
chemical_list: D008372:Manure; D012987:Soil; D012989:Soil Pollutants; D010758:Phosphorus