title: Distribution of phosphorus in manure slurry and its infiltration after application to soils.
abstract: Computer models help identify agricultural areas where P transport potential is high, but commonly used models do not simulate surface application of manures and P transport from manures to runoff. As part of an effort to model such P transport, we conducted manure slurry separation and soil infiltration experiments to determine how much slurry P infiltrates into soil after application but before rain, thus becoming less available to runoff. We applied dairy and swine slurry to soil columns and after both 24 and 96 h analyzed solids remaining on the soil surface for dry matter, total phosphorus (TP), and water-extractable inorganic (WEIP) and organic (WEOP) phosphorus. We analyzed underlying soils for Mehlich-3 and water-extractable P. We also conducted slurry separation experiments by sieving, centrifuging, and suction-filtering to determine which method could easily estimate slurry P infiltration into soils. About 20% of slurry solids and 40 to 65% of slurry TP and WEIP infiltrated into soil after application, rendering this P less available to transport in runoff. Slurry separation by suction-filtering through a screen with 0.75-mm-diameter openings was the best method to estimate this slurry P infiltration. Measured quantities of manure WEOP changed too much during experiments to estimate WEOP infiltration into soil or what separation method can approximate infiltration. Applying slurries to soils always increased soil P in the top 0 to 1 cm of soil, frequently in the 1- to 2-cm depth of soil, but rarely below 2 cm. Future research should use soils with coarser texture or large macropores, and slurry with low dry matter content (1-2%).
authors.affiliation: USDA-Agricultural Research Service, Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA 16802-3702, USA. peter.vadas@ars.usda.gov
authors.forename: Peter A
authors.initials: PA
authors.lastname: Vadas
mesh_terms: D000818:Animals; D002417:Cattle; D005308:Fertilizers; D008372:Manure; D010758:Phosphorus / Q000032:analysis*; D012987:Soil; D012989:Soil Pollutants / Q000032:analysis; D013552:Swine
chemical_list: D005308:Fertilizers; D008372:Manure; D012987:Soil; D012989:Soil Pollutants; D010758:Phosphorus