title: Long-term manure application effects on phosphorus speciation, kinetics and distribution in highly weathered agricultural soils.
abstract: Phosphorus (P) K-edge XANES and Fe K-edge EXAFS spectroscopies along with sequential P chemical fractionation and desorption kinetics experiments, were employed to provide micro- and macro-scale information on the long-term fate of manure application on the solid-state speciation, kinetics and distribution of P in highly weathered agricultural soils of southern Brazil. Soil test P values ranged from 7.3 up to 16.5 times as much higher than the reference soil. A sharp increase in amorphous Fe and Al amounts were observed as an effect of the consecutive application of manures. Whereas our results showed that the P sorption capacity of some manured soils was not significantly affected, P risk assessment indices indicated that P losses should be expected, likely due to the excessive manure rates applied to the soils. The much higher contents of amorphous Fe and Al (hydr)oxides (55% and 80% increase with respect to the reference soil, respectively) in manured soils seem to have counterbalanced the inhibiting effect of soil organic matter on P sorption by creating additional P sorption sites. Accordingly, the newly created P sorbing surfaces were important to prevent an even larger P loss potential. Phosphorus K-edge XANES lent complimentary hints on the loss of crystallinity and transformation of originally present Fe-P minerals into poorly crystalline ones as an effect of manuring, whereas Fe K-edge EXAFS provided insights into the structural changes underwent in the soils upon manure application and soil management.
authors.affiliation: Plant & Soil Sciences Department, University of Delaware, Newark, DE 19716-000, United States. Electronic address: daltonabdala@gmail.com.
authors.forename: Dalton Belchior
authors.initials: DB
authors.lastname: Abdala
authors.affiliation: Soil Science Department, Federal University of Viçosa, Viçosa, MG 36570-000, Brazil.
authors.forename: Ivo Ribeiro
authors.initials: IR
authors.lastname: da Silva
authors.affiliation: Soil Science Department, Federal University of Viçosa, Viçosa, MG 36570-000, Brazil.
authors.forename: Leonardus
authors.initials: L
authors.lastname: Vergütz
authors.affiliation: Plant & Soil Sciences Department, University of Delaware, Newark, DE 19716-000, United States.
authors.forename: Donald Lewis
authors.initials: DL
authors.lastname: Sparks
mesh_terms: D000383:Agriculture / Q000379:methods; D001938:Brazil; D007700:Kinetics; D008372:Manure / Q000032:analysis*; D010758:Phosphorus / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008372:Manure; D012987:Soil; D010758:Phosphorus
keywords: Degree of soil phosphorus saturation; Fe K-edge EXAFS; Phosphorus K-edge XANES; Phosphorus desorption kinetics; Phosphorus loss potential; Phosphorus solid-state speciation