Analysis of Phosphorus in Sequentially Extracted Grassland Soils Using Solid State NMR

Abstract

Sequential extraction and solid state ³¹P NMR spectroscopy were used to investigate the relative solubility of phosphorus (P) in a series of soils under permanent grassland in New Zealand. This involved comparing spectra of unextracted soil with residual soil after extraction with 1 M NH₄Cl–0.1 M NaOH and 1 M NH₄Cl–0.1 M NaOH–0.5 M H₂SO₄. Results confirmed that alkali extraction selectively removed P associated with aluminum (Al) and iron (Fe), while subsequent extraction with acid removed calcium (Ca)-P. This indicates that fractionation schemes can be used to isolate categories of P species involved in soil P cycling and the added value of solid state NMR for the analysis of soil P species in situ.

Acknowledgments

This work was supported in part by grants from the Foundation for Research, Science and Technology, (New Zealand, contract, AGRX0002), AGMARDT (New Zealand), St. John's College (Cambridge University, Cambridge, UK), Lincoln University (New Zealand), and grant AO 6462 from the UK Biotechnology and Biological Sciences Research Council. The NMR instrumentation was provided by the University of London Intercollegiate Research scheme, and is located at University College (Bruker MSL 300, Dr. A.E. Aliev).