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Organic Phosphate Transport and Hydrolysis in Soil: Theoretical and Experimental Evaluation
Author(s) -
Castro C. L.,
Rolston D. E.
Publication year - 1977
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/sssaj1977.03615995004100060014x
Subject(s) - adsorption , chemistry , desorption , sorption , phosphate , hydrolysis , loam , aqueous solution , chromatography , inorganic chemistry , soil water , organic chemistry , geology , soil science
An understanding of the movement, hydrolysis, and retention of organic phosphates in soils is necessary to evaluate possible advantages of the compounds as fertilizers, based upon their characteristic of increased vertical movement over that of inorganic phosphates when applied with irrigation water. Pulses of chloride and glycerophosphate were applied to 4‐, 10‐, and 20‐cm long Panoche clay loam (Typic Torriorthents) soil columns maintained slightly water‐unsaturated (soil‐water pressure = −0.018 bar). The concentration of glycerophosphate in the pulse applications varied from 386 to 1,110 ppm P. An analytical solution assuming first‐order kinetics and a reversible, linear isotherm for glycerophosphate hydrolysis and sorption, respectively, was compared with measured glycerophosphate concentrations in the column effluent. An analytical solution of the coupled equations for simultaneous transport of organic phosphate and orthophosphate assuming a linear, reversible isotherm for orthophosphate adsorption is given. This solution was compared with measured orthophosphate concentrations in the effluent from a continuous application of glycerophosphate to a 2‐cm long column. Organic phosphate adsorption on soil colloids was effectively separated from organic phosphate hydrolysis using displacement techniques. The magnitude of the fitted, first‐order constant for hydrolysis was dependent upon the initial concentration of the influent solution indicating that first‐order kinetics may not be applicable for high organic phosphate concentrations. The magnitude of the fitted, adsorption‐desorption constant for glycerophosphate was dependent upon concentration indicating that adsorption‐desorption was nonlinear. The nonlinearity of glycerophosphate adsorption‐desorption was verified from an equilibrium, adsorption isotherm. The magnitude of the fitted orthophosphate sorption constant for coupled glycerophosphate and orthophosphate transport was considerably larger than that determined from a 6‐day equilibrium adsorption isotherm.