31Phosphorus‐Nuclear magnetic resonance analysis in extracts of a phosphorus‐enriched volcanic soil of Chile

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Abstract
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 31phosphorus‐nuclear magnetic resonance (31P‐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 31P‐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.