title: Differential release of manure-borne bioactive phosphorus forms to runoff and leachate under simulated rain.
abstract: Limited information exists on the unhindered release of bioactive phosphorus (P) from a manure layer to model the partitioning and transport of component P forms before they reach an underlying soil. Rain simulations were conducted to quantify effects of intensity (30, 60, and 90 mm h-1) on P release from an application of 60 Mg ha-1of dairy manure. Runoff contained water-extractable- (WEP), exchangeable and enzyme-labile bioactive P (TBIOP), in contrast to the operationally defined "dissolved-reactive P" form. The released P concentrations and flow-weighed mass loads were described by the log-normal probability density function. At a reference condition of 30 mm h-1and maintaining the surface at a 5% incline, runoff was minimal, and WEP accounted for 20.9% of leached total P (TP) concentrations, with an additional 25-30% as exchangeable and enzyme-labile bioactive P over the 1-h simulation. On a 20% incline, increased intensity accelerated occurrence of concentrationmaxand shifted the skewed P concentration distribution more to the left. Differences in trends of WEP, TBIOP, or net enzyme-labile P (PHPo) cumulative mass released per unit mass of manure between intensities were attributable to the higher frequency of raindrops striking the manure layer, thus increasing detachment and load of colloidal PHPoof the water phases. Thus, detailed knowledge of manure physical characteristics, bioactive P distribution in relation to rain intensity, and attainment of steady-state of water fluxes were critical factors in improved prediction of partitioning and movement of manure-borne P under rainfall.
authors.affiliation: USDA, ARS, Beltsville Agricultural Research Center, Environmental Microbial Food Safety Laboratory, Beltsville, MD 20705, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Blaustein
authors.affiliation: USDA, ARS, Beltsville Agricultural Research Center, Crop Systems and Global Change Laboratory, Beltsville, MD 20705, USA. Electronic address: thanh.dao@ars.usda.gov.
authors.forename: Thanh H
authors.initials: TH
authors.lastname: Dao
authors.affiliation: USDA, ARS, Beltsville Agricultural Research Center, Environmental Microbial Food Safety Laboratory, Beltsville, MD 20705, USA.
authors.forename: Y A
authors.initials: YA
authors.lastname: Pachepsky
authors.affiliation: USDA, ARS, Beltsville Agricultural Research Center, Environmental Microbial Food Safety Laboratory, Beltsville, MD 20705, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Shelton
mesh_terms: D008372:Manure; D010758:Phosphorus; D011891:Rain; D012987:Soil; D012989:Soil Pollutants; D014872:Water Movements
chemical_list: D008372:Manure; D012987:Soil; D012989:Soil Pollutants; D010758:Phosphorus
keywords: Bioactive phosphorus forms; Enzyme-labile phosphorus; Log-normal probability density function; Manure phosphorus in runoff; Organic phosphorus; Stochastic transport of phosphorus