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

Author
item CADE-MENUN, BARBARA - Agriculture And Agri-Food Canada
item He, Zhongqi
item DOU, ZHENGXIA - University Of Pennsylvania

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2015
Publication Date: 7/17/2015
Citation: Cade-Menun, B.J., He, Z., 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):1698-1712.

Interpretive Summary: Phosphorus (P) loss from animal manure through surface runoff or subsurface drainage involves dissolution and transport processes, which depend on not only the total amount but also the solubility and other chemical properties of P in manure. Thus, knowing the P forms in manure is helpful in understanding P loss mechanism. However, there has been a scarcity of published research examining P chemical characteristics and relevant environmental implications as affected by different extraction procedures, particularly in water extracts, or as a result of different animal feeding programs. This study quantified P forms in different extracting solutions of dairy fecal samples. Per the results in this study, we suggest that extraction with water may be a better choice for studies monitoring labile manure P and potential environmental impact. Other more complex extracting solutions are good choices for characterizing and quantifying all the P forms in manure and fecal samples.

Technical 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 EDTA (NaOH-EDTA), for the profile of P compounds in two dairy fecal samples. Phosphorus extracted was 35% for water, and 80-100% for NaAc-SD and NaOH-EDTA. Water extracted a higher 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.