(31)PHOSPHORUS NUCLEAR-MAGNETIC-RESONANCE ANALYSIS IN EXTRACTS OF A PHOSPHORUS-ENRICHED VOLCANIC SOIL OF CHILE

The nature of organic and inorganic phosphorus (P) in fertilized and u nfertilized samples of Vilcun soil, a Chilean medial mesic typic Dystr andept which was studied through (31)phosphorus-nuclear magnetic reson ance (P-31-NMR) analysis carried out on a single alkaline extraction. The total P contents ranged from 1,506 mg P kg(-1) (B horizon, unferti lized soil) to 7,541 mg P kg(-1) (A horizon, fertilized soil). The mag nitude of the P signal (SEM-EDAX results) appears to be related to tha t of the iron (Fe) signal. Signals of P-31-NMR spectra are attributabl e to inorganic orthophosphate, and orthophosphate monoesters and diest ers. No important differences between horizons were observed. Apparent ly in this soil, P are mainly associated with iron oxides and organic matter. The organic P forms were not readily subjected to mineralizati on.