Long-term manure application effects on phosphorus speciation, kinetics and distribution in highly weathered agricultural soils

• Published in: Chemosphere (Oxford) Vol. 119; pp. 504 - 514
• Main Authors: Abdala, Dalton Belchior, da Silva, Ivo Ribeiro, Vergütz, Leonardus, Sparks, Donald Lewis
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-01-2015
• Subjects: Agriculture - methods; Aluminum; Brazil; Degree of soil phosphorus saturation; Fe K-edge EXAFS; Iron; Kinetics; Manure; Manure - analysis; Phosphorus; Phosphorus - chemistry; Phosphorus desorption kinetics; Phosphorus K-edge XANES; Phosphorus loss potential; Phosphorus solid-state speciation; Soil - chemistry; Soils; Sorption; Speciation; Transformations; X-Ray Absorption Spectroscopy; Fe K-edge EXAFS; Phosphorus solid-state speciation; Degree of soil phosphorus saturation; Phosphorus desorption kinetics; Phosphorus loss potential; Phosphorus K-edge XANES
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2014.07.029

•Importance of long-term manure application on soil mineralogy.•Changes in soil mineralogy followed by long-term application of manures.•P and Fe K-edge XAFS spectroscopic analysis of diagnostic spectral features of manured soils.•P cycling in manured soils as assessed by P desorption kinetics.•Questionable sensitivity of P sorption indices to predict P losses.
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.