title: Investigation of soil legacy phosphorus transformation in long-term agricultural fields using sequential fractionation, P K-edge XANES and solution P NMR spectroscopy.
abstract: 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)P 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.
authors.affiliation: Visiting Scientist, Semiarid Prairie Agricultural Research Centre (SPARC), Agriculture and Agri-Food Canada , Box 1030, Swift Current, Saskatchewan S9H 3X2 Canada.
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Hu
authors.forename: Jianjun
authors.initials: J
authors.lastname: Yang
authors.forename: Dalel
authors.initials: D
authors.lastname: Abdi
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Cade-Menun
mesh_terms: D000383:Agriculture; D000535:Aluminum; D005591:Chemical Fractionation; D009682:Magnetic Resonance Spectroscopy; D010087:Oxides / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry*; D010833:Phytic Acid / Q000032:analysis; D012525:Saskatchewan; D012987:Soil / Q000737:chemistry*; D014908:Triticum; D060753:Water Quality; D056928:X-Ray Absorption Spectroscopy
chemical_list: D010087:Oxides; D010710:Phosphates; D012987:Soil; D010758:Phosphorus; D010833:Phytic Acid; D000535:Aluminum