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Sequestration of Phosphorus‐Binding Cations by Complexing Compounds is not a Viable Mechanism to Increase Phosphorus Efficiency
Author(s) -
Degryse Fien,
Ajiboye Babasola,
Armstrong Roger D.,
McLaughlin Mike J.
Publication year - 2013
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/sssaj2013.05.0165
Subject(s) - chemistry , fertilizer , soil water , phosphorus , phosphate , ligand (biochemistry) , diffusive gradients in thin films , solubility , leaching (pedology) , chelation , inorganic chemistry , environmental chemistry , nuclear chemistry , organic chemistry , metal , biochemistry , soil science , geology , receptor
There is increasing interest in enhancing the efficiency of P fertilizers or mobilizing fixed P from soil. Cation‐complexing ligands are claimed to increase availability of fertilizer‐applied or soil P through sequestration of cations (Fe, Al, Ca) that bind P strongly. We assessed the effect of ligand addition on mobility and availability of P in four soils, using a large range of cation‐complexing compounds, in batch experiments without or with added P, and found only small effects of these compounds on P solubility. Selected compounds, including two commercial polymer coatings, coated on granular monoammonium phosphate (MAP) and an organic‐complexed form of single superphosphate (SSP) fertilizer were tested in diffusion experiments and in a pot trial and compared with conventional MAP or SSP. The ligand treatments, at a 1% coating rate on granular fertilizers, did not significantly affect P diffusion. The only significant difference was between the MAP and SSP treatments, with a lower rate of diffusion from SSP, presumably because of enhanced Ca–P precipitation. Only at very high, commercially unrealistic coating rates (up to 100%) of a dicarboxylic copolymer did P solution concentrations close to the granule increase in an Oxisol, but not in a calcareous soil. The pot trial also showed no effect of the ligand treatments at a 1% coating rate in any of the three soils tested. These results, as well as theoretical considerations, indicate that complexation of P‐binding cations is unlikely to be an economically viable process to either release P from stored forms in soil or to increase efficiency of added fertilizer P.