Investigation of soil legacy phosphorus transformations in long-term agricultural fields using sequential fractionation, P K-edge XANES and solution P-NMR spectroscopy.
Liu, J., Hu, Y.F., Yang, J.J., Abdi, D., and Cade-Menun, B.J. (2015). "Investigation of soil legacy phosphorus transformations in long-term agricultural fields using sequential fractionation, P K-edge XANES and solution P-NMR spectroscopy.", Environmental Science & Technology, 49(1), pp. 168-176. doi : 10.1021/es504420n Access to full text
Understanding legacy phosphorus (P) build-up and draw-down from long-term fertilization is essential for effective P management. Using replicated plots from Saskatchewan, Canada, with P fertilization from 1967 to 1995 followed by either P fertilization or P cessation (1995–2010), soil P was characterized in surface and subsurface layers using sequential fractionation, P K-edge X-ray absorption near-edge structure (XANES) and solution 31 nuclear magnetic resonance (P NMR) spectroscopy. Legacy P from a 28-year build-up was sufficient for 15 years of wheat cultivation, resulting in no significant differences in crop yield in 2010. In surface soils, soil test (Olsen) P decreased significantly in unfertilized plots compared with 1995, which was reflected in declining aluminum (hydr)oxide-associated inorganic P by fractionation and XANES. Furthermore, XANES analysis revealed a decrease of calcium-associated P in 2010-unfertilized soils at both depths and an increase of Fe (hydr)oxides-associated P in the 2010-fertilized and -unfertilized surface soils relative to the 1995 soils. Increased total organic P and orthophosphate diesters by P NMR and accumulated inositol hexaphosphate by XANES were observed in surface soils with P fertilization cessation. In subsurface soils, few legacy P transformations were detected. These results provide important information about legacy P to improve agricultural sustainability while mitigating water quality deterioration.
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