101360 Solubilization of Phosphate from Poorly Crystalline Fe and Al Hydroxides By AVAIL® Copolymer.

Poster Number 467-317

See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Soil Chemistry Poster

Wednesday, November 9, 2016
Phoenix Convention Center North, Exhibit Hall CDE

Sarah Doydora, Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC and Dean Hesterberg, North Carolina State University, Raleigh, NC
Abstract:
Less than 40% of fertilizer phosphate applied to soils is 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 between Fe(III) and Al(III) in 1:1 (w:w) mixtures of these solids using P K-edge XANES spectroscopy. With increasing co-additions of AVAIL or P at the levels evaluated, sorption results showed dissolved P increasing up to 0.45 and 1.25 mmol L-1 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. XANES results showed that 72-86% 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 can be used to estimate banded application rates of AVAIL® and P fertilizers on soils with different P sorption capacities.

See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Soil Chemistry Poster