Natural colloidal P and its contribution to plant P uptake
2015
Montalvo, D. | Degryse, F. | McLaughlin, M.
Phosphorus (P) bioavailability depends on its concentration and speciation in solution. Andisols and Oxisols have very low soil solution concentration of free orthophosphate, as they contain high concentrations of strongly P-sorbing minerals (Al/Fe oxyhydroxides, allophanes). Free orthophosphate is the form of P taken up by plants, but it is not the only P species present in the soil solution. Natural colloidal P (P associated with Al, Fe, and organic matter of sizes ranging from 1-1000 nm) constitutes an important fraction of soil solution P in these soils; however, its availability has not been considered. We measured the uptake of P by wheat (Triticum aestivum) from radiolabeled non-filtered (colloid-containing) and 3-kDa filtered (nearly colloid-free) soil-water extracts from Andisols and Oxisols. In the Andisol extracts, P uptake was up to five-fold higher from the non-filtered solutions than the corresponding 3-kDa filtered solutions. In the Oxisol extract, no difference in P uptake between both solutions was observed. Also the diffusional flux of P as measured with the DGT technique was larger in the non-filtered than in the 3-kDa filtered solutions. Our results suggest that colloidal P from Andisols is not chemically inert and contributes to plant uptake of P.
Show more [+] Less [-]Daniela Montalvo, Fien Degryse and Mike J. McLaughlin
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