AbstractAs a first step towards assessing the contribution of organic phosphorus to rice nutrition, the chemical nature of phosphorus in arange of Madagascan rice soils was determined by NaOH–EDTA extraction and solution 31 P nuclear magnetic resonancespectroscopy. A considerable proportion of the extractable phosphorus occurred in organic forms (19–44%), mostly as phosphatemonoesters, with smaller concentrations of DNA. Inositol phosphates were detected in less than half of the soils, despite theirperceived abundance, while phosphate monoesters in the remaining soils consisted of the alkaline hydrolysis products of RNA andphospholipids. Organic phosphorus concentrations were greater in soils rich in organic matter, but there were no apparentdifferences between soils under conventional flooded rice cultivation and the system of rice intensification. Additional experimentsare now required to assess the role of organic phosphorus in the nutrition of rice growing under a range of management and soilconditions.© 2006 Elsevier B.V. All rights reserved.