Phosphorus leaching in a sandy soil as affected by organic and inorganic fertilizer sources

Long-term application of phosphorus (P) to soils as fertilizer or manure can increase the potential for P loss to ground and surface waters. Vertical P transport was investigated in a sandy soil material receiving seven different P fertilizer sources: poultry compost, poultry litter, triple superphosphate [Ca(H(2)PO(4))(2)center dot H(2)O], dairy lagoon liquid, swine lagoon liquid, swine lagoon sludge, and dissolved potassium dihydrogen phosphate (KH(2)PO(4)). The P sources were surface-applied to soil columns (6.35-cm diameter, 10-cm long) at two rates equivalent to 75 and 150 kg total P ha(-1), and columns were intermittently leached with deionized (DI) water. Column effluents were collected for up to 23 pore volumes and analyzed for dissolved reactive phosphorus (DRP) and dissolved organic carbon (DOC). In addition, a P retardation factor was determined for the soil from a P adsorption isotherm. Transport of P through soil columns receiving liquid P sources was simulated by a one-dimensional equilibrium convective-dispersive equation (CDE) based on water-extractable P (WEP) concentrations. Cumulative amounts of DRP leached were linearly related to the amounts of WEP in P source materials (r(2) = 0.87***). The recovery of DRP in the column effluents relative to WEP in the applied materials was 126 +/- 15% (mean +/- standard error) for organic P sources and 66 +/- 2% for inorganic P sources. The use of WEP in the CDE model underpredicted P transport in the columns amended with lagoon liquids compared with dissolved KH(2)PO(4). Results indicated that leaching losses of P from land-applied manures exceed the amounts of WEP in source materials because of organic P mineralization and competitive sorption of DOC. (C) 2011 Elsevier B.V. All rights reserved.