Comparison of phosphorus forms in three extracts of dairy feces by solution 31P NMR analysis.

Cade-Menun, B.J., He, Z.Q., and Dou, Z. (2015). "Comparison of phosphorus forms in three extracts of dairy feces by solution 31P NMR analysis.", Communications in Soil Science and Plant Analysis, 46(13), pp. 1698-1712. doi : 10.1080/00103624.2015.1047512  Access to full text

Abstract

Using solution 31P NMR spectroscopy, we compared three extractants, deionized water, sodium acetate buffer (pH 5.0) with fresh sodium dithionite (NaAc-SD), and 0.25 M NaOH–0.05 M ethylenediaminetetraacetic acid (NaOH-EDTA), for the profile of P compounds in two dairy fecal samples. Phosphorus extracted was 35 percent for water and 80–100 percent for NaAc-SD and NaOH-EDTA. Water extracted a greater proportion of organic P forms, particularly orthophosphate diesters, but a lower proportion of orthophosphate relative to NaOH-EDTA and NaAc-SD. Phosphorus recoveries and spectra were generally similar for NaOH-EDTA and NaAc-SD, but there was increased degradation of polyphosphate to pyrophosphate with NaOH-EDTA, and water, for one sample relative to NaAc-SD. For studies characterizing and quantifying all the P forms in manure and fecal samples, these results suggest that either NaOH-EDTA or NaAc-SD would be a good choice. However, extraction with water may be a better choice for studies monitoring labile manure P and potential environmental impact.

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