Insights into Phosphorus Biogeochemistry from Advanced Molecular Techniques.

Historically, knowledge about phosphorus (P) biogeochemistry has lagged behind that of carbon and nitrogen due to technical limitations. Soil P research has focussed predominantly on inorganic P and P fertilizer needs, ignoring the organic P forms that comprise 50% or more of total P in many soils. Methods for characterizing P were often restricted to sequential fractionation techniques, varying in their chemical specificity, followed by simple colorimetric techniques. However, in the last few decades there have been significant methodological advances, allowing the characterization of P forms with ³¹P nuclear magnetic resonance (NMR) and P K- and L_2,3-edge X-ray absorption near-edge structure (XANES) spectroscopy. These techniques have allowed the majority of P species in soil and environmental samples to be classified into general compound types, and often into specific P forms.  In addition, knowledge about P cycling has improved through research using the ratio of stable oxygen isotopes in phosphate (δ¹⁸O-P). This presentation will review our current understanding of P biogeochemistry, focussing on knowledge gained from the use of advanced techniques. It will also discuss areas where knowledge is still limited, and future research needs.