title: Natural colloidal P and its contribution to plant P uptake.
abstract: 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 to 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 nonfiltered (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 5-fold higher from the nonfiltered 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 nonfiltered 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.
authors.affiliation: †Soil Science, School of Agriculture Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, South Australia 5064, Australia.|‡CSIRO Sustainable Agriculture Flagship, CSIRO Land and Water, PMB 2, Glen Osmond, South Australia 5064, Australia.
authors.forename: Daniela
authors.initials: D
authors.lastname: Montalvo
authors.affiliation: †Soil Science, School of Agriculture Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, South Australia 5064, Australia.
authors.forename: Fien
authors.initials: F
authors.lastname: Degryse
authors.affiliation: †Soil Science, School of Agriculture Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, South Australia 5064, Australia.|‡CSIRO Sustainable Agriculture Flagship, CSIRO Land and Water, PMB 2, Glen Osmond, South Australia 5064, Australia.
authors.forename: Mike J
authors.initials: MJ
authors.lastname: McLaughlin
mesh_terms: D001682:Biological Availability; D003102:Colloids / Q000493:pharmacokinetics; D005374:Filtration; D010710:Phosphates; D010758:Phosphorus / Q000493:pharmacokinetics*; D010944:Plants; D012987:Soil / Q000737:chemistry; D012996:Solutions; D014908:Triticum / Q000187:drug effects / Q000378:metabolism*
chemical_list: D003102:Colloids; D010710:Phosphates; D012987:Soil; D012996:Solutions; D010758:Phosphorus