Abstract

Four procedures were employed to extract phosphorus (P) from volcanic soils for 31 PNMR experiments. The procedures involve 0.5 M NaOH extraction, 0.5 M NaOH and Chelex 100 cation exchange resin extraction, NaOHEDTA extraction, and HClNaOH two step sequential extraction with Chelex 100 clean up. Results showed that inorganicP, monoesterP, diesterP and pyrophosphate were present. Their detection was dependent on the extraction procedure used. The NaOH procedure gives only a broad and vaguely defined signal with poor signal to noise ratio. The incorporation of Chelex 100 in the extraction enhanced the signal to noise ratio and allowed the distinction of inorganicP, monoesterP, diesterP and pyrophosphate. The two step sequential extraction involving HCl, NaOH, and Chelex 100 significantly improve the signal to noise ratio. The NaOHEDTA extraction procedure is efficient only in samples with low OC contents. When soils have low OC content, any of the four extraction procedures can be successfully used. If the OC and the Fe concentration in the extracted solutions are high, the Chelex 100 became essential in clean up the metallic ions. Both the NaOH and Chelex 100 and the HClNaOHChelex produced satisfactory results and the later procedure by far the best resolved spectra. Copyright © Taylor & Francis Group, LLC.