Soil organic phosphorus

Abstract

Abstract Using the resin fractionation procedure developed in Part I, the behaviour of known organic phosphorus compounds added to 0.3M KOH soil extract was determined. With resin having 3–5 per cent cross-linking inositol phosphates, RNA nucleotides and glycerophosphate were quantitatively retained by the resin and could be recovered in good yield, each in different fractions. With resin having 8 per cent cross-linking, >50 per cent of inositol hexaphosphate added to 0.3M KOH soil extract was not retained. The formation of complexes which is presumed responsible for this behaviour must have occurred in less than 40 minutes at room temperature. It is considered possible that complexes of inositol phosphates with soil organic matter may arise during soil extraction and may not necessarily exist in the soil. RNA nucleotide phosphorus was not detected in alkaline soil extracts, but there was strong evidence for inositol hexaphosphate in fraction III. Experiments with P32 showed that the methods described can provide quantitative data on the transformation of soil inorganic and organic phosphorus at the microgramme level. Direct exchange of P32 between inorganic and organic fractions could not be detected. There was a low incorporation of P32 (orthophosphate) into soil organic phosphorus in fresh soil held at 23°C for three weeks.