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Phosphate Solubilization from Poorly Crystalline Iron and Aluminum Hydroxides by AVAIL Copolymer
Author(s) -
Doydora Sarah,
Hesterberg Dean,
Klysubun Wantana
Publication year - 2016
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2016.08.0247
Subject(s) - ferrihydrite , chemistry , sorption , goethite , xanes , hydroxide , phosphate , dissolution , aqueous solution , inorganic chemistry , adsorption , nuclear chemistry , solubility , spectroscopy , organic chemistry , physics , quantum mechanics
Core Ideas Dissolved P increased with increasing co‐additions of AVAIL and P to metal oxides. AVAIL dissolved greater P with Al‐hydroxide than with ferrihydrite. AVAIL had no effect on P bonding distribution between Al(III) and Fe(III) in mixed sorbents. Less than 40% of fertilizer phosphate applied to soils is generally taken up by crops because of strong retention of P by soil solids. Our objective was to determine mechanisms by which AVAIL, a maleic‐itaconic copolymer used as a fertilizer additive, potentially affects retention of applied phosphate, and consequently plant availability. We measured competitive sorption of AVAIL and orthophosphate in aqueous suspensions of ferrihydrite and poorly crystalline Al hydroxide [pxl‐Al(OH) 3 ] at pH 6.2, and characterized phosphate bonding distribution between Fe(III) and Al(III) in 1:1 (w/w) mixtures of these solids using P K‐edge X‐ray absorption near edge structure (XANES) spectroscopy. With increasing co‐additions of AVAIL and P at the levels evaluated, sorption results showed dissolved P increasing up to 0.45 and 1.25 m M for ferrihydrite and pxl‐Al(OH) 3 , respectively, which represented 18 and 34% of added P. Negative relationships between sorbed P and sorbed AVAIL implied a competitive adsorption mechanism between these two ligands, and solubilization of Fe by AVAIL indicated complexometric dissolution of ferrihydrite. The XANES results showed that 72 to 86% of sorbed P was bonded with Al(III) in the ferrihydrite/pxl‐Al(OH) 3 mixtures, with only a minor (<15%) effect of AVAIL apparent when P was applied at the two levels tested in this study. Our results suggest that optimized AVAIL application rates for enhancing crop availability of P would depend on soil sorption characteristics and the soil content of residual P relative to its soil sorption capacity.