(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 unfertilized samples of Vilcun soil, a Chilean medial mesic typic Dystrandept which was studied through (31)phosphorus-nuclear magnetic resonance (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, unfertilized soil) to 7,541 mg P kg(-1) (A horizon, fertilized soil). The magnitude of the P signal (SEM-EDAX results) appears to be related to that of the iron (Fe) signal. Signals of P-31-NMR spectra are attributable to inorganic orthophosphate, and orthophosphate monoesters and diesters. No important differences between horizons were observed. Apparently in this soil, P are mainly associated with iron oxides and organic matter. The organic P forms were not readily subjected to mineralization.