title: Solid-Phase Speciation and Solubility of Phosphorus in an Acid Sulfate Paddy Soil during Soil Reduction and Reoxidation as Affected by Oil Palm Ash and Biochar.
abstract: Understanding phosphorus (P) speciation and how redox conditions control P solubility in acid sulfate paddy soils with limited P availability is crucial for improving soil P availability. We examined P speciation and extractability in an acid sulfate paddy soil incorporated with oil palm ash (OPA) and biochar (OPB) during soil reduction and subsequent oxidation. Phosphorus K-edge X-ray absorption near edge structure (XANES) spectra of the soil samples revealed that P in the soil mainly occurred as P adsorbed to ferrihydrite and P adsorbed to gibbsite. During soil reduction, gibbsite-bound P was transformed into variscite, which was back-transformed to gibbsite-bound P during soil reoxidation. Sequential extraction results confirmed the dominance of Fe/Al (hydr)oxides-bound P (average 72%) in the soils. The OPA incorporation increased the exchangeable P pool concurring with the decrease in gibbsite-bound P. The OPB incorporation enhanced the dissolved P from the residual pool presumably due to electron shuttling of biochar with Fe(III) minerals during soil reduction. Our results highlight P dynamics in paddy soils, which are of immense importance for effective P-management strategies in rice cultivation.
authors.affiliation: Department of Soil Science, Faculty of Agriculture, Kasetsart University , Bangkok 10900, Thailand.
authors.forename: Worachart
authors.identifier: http://orcid.org/0000-0002-9258-4335
authors.initials: W
authors.lastname: Wisawapipat
authors.affiliation: Department of Soil Science, Faculty of Agriculture, Kasetsart University , Bangkok 10900, Thailand.
authors.forename: Kamolchanok
authors.initials: K
authors.lastname: Charoensri
authors.affiliation: Department of Soil Science, Faculty of Agriculture, Kasetsart University , Bangkok 10900, Thailand.
authors.forename: Jirawat
authors.initials: J
authors.lastname: Runglerttrakoolchai
mesh_terms: D000327:Adsorption; D000383:Agriculture; D002606:Charcoal / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D012275:Oryza / Q000254:growth & development; D010084:Oxidation-Reduction; D000073878:Palm Oil; D010758:Phosphorus / Q000737:chemistry*; D010938:Plant Oils / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012995:Solubility; D013431:Sulfates / Q000737:chemistry*
chemical_list: D010938:Plant Oils; D012987:Soil; D013431:Sulfates; C540010:biochar; D002606:Charcoal; D010758:Phosphorus; D000073878:Palm Oil
keywords: XANES; XAS; phosphorus speciation; redox; rice; sequential extraction