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Organic Acids Regulation of Chemical–Microbial Phosphorus Transformations in Soils
journal contribution
posted on 2016-10-04, 00:00 authored by Daniel Menezes-Blackburn, Cecilia Paredes, Hao Zhang, Courtney D. Giles, Tegan Darch, Marc Stutter, Timothy
S. George, Charles Shand, David Lumsdon, Patricia Cooper, Renate Wendler, Lawrie Brown, Martin Blackwell, Catherine Wearing, Philip M. HaygarthWe
have used an integrated approach to study the mobility of inorganic
phosphorus (P) from soil solid phase as well as the microbial biomass
P and respiration at increasing doses of citric and oxalic acid in
two different soils with contrasting agronomic P status. Citric or
oxalic acids significantly increased soil solution P concentrations
for doses over 2 mmol kg–1. However, low organic
acid doses (<2 mmol kg–1) were associated with
a steep increase in microbial biomass P, which was not seen for higher
doses. In both soils, treatment with the tribasic citric acid led
to a greater increase in soil solution P than the dibasic oxalic acid,
likely due to the rapid degrading of oxalic acids in soils. After
equilibration of soils with citric or oxalic acids, the adsorbed-to-solution
distribution coefficient (Kd) and desorption
rate constants (k–1) decreased
whereas an increase in the response time of solution P equilibration
(Tc) was observed. The extent of this
effect was shown to be both soil and organic acid specific. Our results
illustrate the critical thresholds of organic acid concentration necessary
to mobilize sorbed and precipitated P, bringing new insight on how
the exudation of organic acids regulate chemical–microbial
soil phosphorus transformations.