CHARACTERIZATION OF PHOSPHORUS FRACTIONS IN SURFACE HORIZONS OF SOILS FROM GALICIA (NW SPAIN) BY P-31 NMR-SPECTROSCOPY

31P NMR spectroscopy was used to study the P fractions in NaOH extracts of surface mineral horizons of soils from Galicia (N.W. Spain). Mono and diesterphosphate dominated in all soils; phosphonates were present under cold and wet conditions. Rankers, Cambisols and Podzols differ in their diester-to-monoester ratio and in the percentage of the NaOH soluble organic P. These results and those for a Rendzina and a Gleysol show a relationship between soil genesis and the forms of organic P present. The relationship between bicarbonate-extractable organic P and the diester content of the soils confirms the nature of labile organic P in these soils and explains the poor correlation between labile organic P and phosphomonoesterase activity. © 1990.