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Complementary phosphorus speciation in agricultural soils by sequential fractionation, solution <sup>31</sup>P nuclear magnetic resonance, and phosphorus K-edge X-ray absorption near-edge structure spectroscopy

Liu, J., Yang, J., Cade-Menun, B.J., Liang, X., Hu, Y., Liu, C.W., Zhao, Y., Li, L., Shi, J. (2013). Complementary phosphorus speciation in agricultural soils by sequential fractionation, solution <sup>31</sup>P nuclear magnetic resonance, and phosphorus K-edge X-ray absorption near-edge structure spectroscopy, 42(6), 1763-1770. http://dx.doi.org/10.2134/jeq2013.04.0127

Abstract

Ultisols in China need phosphorus (P) fertilization to sustaincrop production but are prone to P loss in runoff. Balancing Pinputs and loss requires detailed information about soil P formsbecause P speciation influences P cycling. Analytical methodsvary in the information they provide on P speciation; thus, weused sequential fractionation (SF), solution 31P nuclear magneticresonance (P-NMR), and P K-edge X-ray absorption near-edgestructure (XANES) spectroscopy to investigate organic P (Po) andinorganic P (Pi) species in Chinese Ultisols managed for differentcrops and with different fertilizer inputs in the first study to combinethese techniques to characterize soil P. Sequential fractionationshowed that moderately labile NaOH-P was the largest P poolin these soils, Po varied from 20 to 47%, and residual P rangedfrom 9 to 31%. Deoxyribonucleic acid (1-5%) and myo-inositolhexakisphosphate (myo-IHP, 4-10%) were the major Po formsfrom P-NMR. Orthophosphate diesters determined by NMR weresignificantly correlated with labile NaHCO3-Po in SF (r < 0.981;P > 0.001). Soil Pi was shown to be predominantly associated withiron and soluble calcium (Ca) by XANES. Furthermore, XANESidentified hydroxyapatite in the soil receiving the highest rates ofCa-phosphate fertilizer, which had the highest HCl-P pool by SF,and also identified IHP (7%) in the soil with the highest proportionof myo-IHP from P-NMR. These results strongly suggest that acombined use of SF, solution P-NMR, and P K-edge XANESspectroscopy will provide the comprehensive information about soilP species needed for effective soil P management. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

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