31P-NMR analysis of phosphorus compounds in extracts of surface soils from selected karri (Eucalyptus diversicolor F. Muell.) forests

TLDR: In this paper, a range of highly-weathered Karri forest soils were extracted using a chelating, cation exchange resin in preference to NaOH extraction as the former proved more suitable for use with NMR analysis.

Abstract: Phosphorus compounds in concentrated extracts of a range of highly-weathered Karri forest soils were identified and quantified by 31 P-NMR. The extracts were prepared using a chelating, cation-exchange resin in preference to NaOH extraction as the former proved more suitable for use with NMR analysis. Concentrations of alkali- or resin-extractable P in the soils of this study were about an order of magnitude less than in soils which have been used in previous 31 P-NMR studies of soil-P. As forest age increased, the proportion of extracted-P present in forms other than inorganic orthophosphate also increased. Monoester-P was the largest fraction of the extracted organic-P followed by diesters, pyrophosphate and traces of polyphosphates and phosphonates. Sugar phosphates (e.g. glucose-6-phosphate or ribose-5-phosphate), as well as inositol-P and choline-P, resonate at frequencies similar to those measured for soil monoesters. Buffered cation exchange resins may be useful in future studies of highly-weathered soils.