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Analysis of Potentially Mobile Phosphorus in Arable Soils Using Solid State Nuclear Magnetic Resonance

^a USDA-ARS Pasture Systems and Watershed Management Research Laboratory, University Park, PA 16802-3702
^b Soil, Plant & Ecological Sciences Division, P.O. Box 84, Lincoln University, Canterbury, New Zealand
^c IACR, Rothamsted, Harpenden, Hertfordshire AL5 2JQ, UK

View larger version (17K): [in a new window]   Fig. 1. The relationship between Olsen P and CaCl2–P for Barnfield soils from the 1958 sampling (adapted from McDowell et al., 2001). The arrow indicates the threshold or change point at 59 mg Olsen P kg-1. Filled circles indicate the samples used here (± standard errors).

View larger version (28K): [in a new window]   Fig. 2. High-power decoupling with magic angle spinning (HPDec–MAS) nuclear magnetic resonance (NMR) (A) and cross polarization with magic angle spinning (CP–MAS) (B) spectra of Soil 1 before extraction (control) and after extraction with either 0.01 M CaCl2 or water. Dashed and solid peaks represent Ca-P and Al-P species, respectively (see Fig. 3, Table 2). Resonances marked ssb are spinning sidebands.

View larger version (26K): [in a new window]   Fig. 3. High-power decoupling with magic angle spinning (HPDec–MAS) nuclear magnetic resonance (NMR) (A) and cross polarization with magic angle spinning (CP–MAS) (B) spectra of Soil 2 before extraction (control) and after extraction with either 0.01 M CaCl2 or water. Dashed and solid peaks represent Ca-P and Al-P species, respectively. Resonances marked ssb are spinning sidebands.

View larger version (26K): [in a new window]   Fig. 4. High-power decoupling with magic angle spinning (HPDec–MAS) nuclear magnetic resonance (NMR) (A) and cross polarization with magic angle spinning (CP–MAS) (B) spectra of Soil 3 before extraction (control) and after extraction with either 0.01 M CaCl2 or water. Dashed and solid peaks represent Ca-P and Al-P species, respectively (see Fig. 3a, Table 2). Resonances marked ssb are spinning sidebands.