title: Anoxia-induced release of colloid- and nanoparticle-bound phosphorus in grassland soils.
abstract: Particle-facilitated transport is a key mechanism of phosphorus (P) loss in agroecosystems. We assessed contributions of colloid- and nanoparticle-bound P (nPP; 1-415 nm) to total P released from grassland soils receiving biannual poultry litter applications since 1995. In laboratory incubations, soils were subjected to 7 days of anoxic conditions or equilibrated at pH 6 and 8 under oxic conditions and then the extract was size fractionated by differential centrifugation/ultrafiltration for analysis of P, Al, Fe, Si, Ti, and Ca. Selected samples were characterized by transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) and field flow fractionation (FFF-ICP-MS). Particles released were present as nanoaggregates with a mean diameter of 200-250 nm, composed of ~50-nm aluminosilicate flakes studded with Fe and Ti-rich clusters (<10 nm) that contained most of the P detected by EDS. Anoxic incubation of stimulated nPP release with seasonally saturated soils released more nPP and Fe(2+)(aq) than well-drained soils; whereas, nonreductive particle dispersion, accomplished by raising the pH, yielded no increase in nPP release. This suggests Fe acts as a cementing agent, binding to the bulk soil P-bearing colloids that can be released during reducing conditions. Furthermore, it suggests prior periodic exposure to anoxic conditions increases susceptibility to redox-induced P mobilization.
authors.affiliation: Department of Crop and Soil Sciences, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: R
authors.initials: R
authors.lastname: Henderson
authors.forename: N
authors.initials: N
authors.lastname: Kabengi
authors.forename: N
authors.initials: N
authors.lastname: Mantripragada
authors.forename: M
authors.initials: M
authors.lastname: Cabrera
authors.forename: S
authors.initials: S
authors.lastname: Hassan
authors.forename: A
authors.initials: A
authors.lastname: Thompson
mesh_terms: D000818:Animals; D003102:Colloids / Q000737:chemistry*; D031744:Cynodon; D005308:Fertilizers; D031751:Festuca; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D008372:Manure; D008670:Metals / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry; D011200:Poultry; D012987:Soil / Q000737:chemistry*
chemical_list: D003102:Colloids; D005308:Fertilizers; D006878:Hydroxides; D008372:Manure; D008670:Metals; D017680:Potassium Compounds; D012987:Soil; D010758:Phosphorus; D010100:Oxygen; C029943:potassium hydroxide