| Summary: | The nature and distribution of phosphorus in soils has been reviewed with particular attention to organic forms. Chromatographic studies by various workers indicate that a major part of the organic P in many soils consists of inositol phosphates (I.P.). Several stereoisomers of inositol (hexahydroxycyclohexane) have been identified but the chief one found in soils is the myo-form and the whole range of esters from lP. to lPg has been detectedbut the ones most abundant in soils are IP5+. A major problem in research on the subject is to extract the various forms without degradation of the more labile constituents and then to isolate them free of contaminating materials. It was found that when soils are extracted with boiling formic acid or with formic acid/water or formic acid/acetylacetone solutions most of the soil P remained undissolved in the residue due to absorption or precipitation by polyvalent metal ions. . A brief boiling with 6m HC1 dissolved most of inorganic and the organic P from a clay loam, with full recovery of added lPg biit the P in a sandy loam was only partially dissolved. The latter soil contained acid soluble titanium minerals and Til,+ precipitates lPg completely from 6m HC1. A short boiling with 6M HCl/0.5 HP solution containing 0.16m T1CI4. dissolved most of the inorganic P from both soils while the unhydrolysed organic P was mostly retained in the soil residues., being precipitated by Ti. Inclusion of HP to form TiFg2- with half the Ti prevented precipitation of inorganic P by Zr. Hie organic P was dissolved from the soil residues by shaking with 3M HC1 + cupferron to precipitate Ti and it was then recovered by precipitation with Ba from an ethanolic/ethanolamine solution at pH 9 Chromatographic studies confirmed that most of this material was IP5 + lPg with, small . amounts of lower esters, and some unidentified organic P from the sand;/- loam. The procedure evolved is' simple to operate and should prove useful for further detailed stxidies of the organic P in soils.
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