Leachate Phosphorus Fractionation Study of Poultry Manure-Amended Vermont Soil.

Understanding the behavior of particulate and dissolved P fractions in manured Vermont soils will contribute to agricultural and surface water management strategies. Three columns packed with sandy loam soils and amended with poultry manure were irrigated weekly with one pore volume (2.3L) of distilled water (pH 5, H₂SO₄) for 10 weeks. Filtered leachate fractions (0.45um) were analyzed for molybdate-reactive-P (MRP) and Total Dissolved P (TDP) and metals (Ca, Mg, Fe, Al, Mn) using ICP-OES. Total P (TP) and metals of whole, persulfate-digested leachate were determined using ICP-OES. Leachate P fractions were defined as: (1) Dissolved Unreactive P (DUP=TDP-MRP), and (2) Total Particulate P (TPP=TP-TDP). The results of this study suggest that in similar soil-irrigation systems:  (1) Dissolved metals (Ca, Mg, Fe, Al) will be leached within the first irrigation event, while TDP will exit the system later (week 4) as carbonate- or sulfate-associated-P; (2) the majority of particulate-P leached will be associated with the Al- or Fe-metals; (3) DUP will decrease by 30 percent of TDP over 10 weeks. The timeline of this study suggests that TP lost (65.4±2.7 mg) within the first 10 weeks of leaching will occur in the forms of TPP(41%) and TDP(22% DUP+37% MRP).