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United States Department of Agriculture

Agricultural Research Service

Title: Characterization of Labile P Forms in Fresh Dairy Manure under Mild Assay Conditions

Authors
item HE, ZHONGQI
item Toor, Gurpal - UNIV OF DELAWARE
item Honeycutt, Charles
item Sims, J Thomas - UNIV OF DELAWARE

Submitted to: Organic P Workshop
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 2004
Publication Date: August 15, 2004
Citation: He, Z., Toor, G.S., Honeycutt, C.W., Sims, J. 2004. Characterization of labile p forms in fresh dairy manure under mild assay conditions. Organic P Workshop. August 16-19, 2004. Wageningen, The Netherlands. Page 59

Technical Abstract: Characterizing labile P forms in animal manure is a challenge due to their susceptibility to hydrolysis. Harsh assay conditions commonly applied for characterizing P, such as sequential fractionation and P-31 NMR analysis, can underestimate labile P in animal manure. In this study, we characterized dairy manure P under relatively mild assay conditions. Fresh dairy manure was separated into soluble and residual components. The hydrolyzable organic P in these fractions was then characterized by enzymatic hydrolysis at pH 5.0 and categorized as simple monoester P, polynucleotide P, phytate-like P, and nonhydrolysable P. Autoclaving released residual P in a level similar to that observed with spontaneous hydrolysis over 54 h. Ultrasonication, intended to release inorganic (Pi) and organic P (Po) trapped in the manure matrix, released little residual P. About 75% of total manure P was characterized by the approach used. The remaining 25% could be regarded as recalcitrant P. In water extracts, 77% was Pi, 11% hydrolyzable Po and 12% enzymatically nonhydrolyzable Po. In the residual resuspension, 25% was spontaneous labile P, 32% was simple monoester P, 7% was polynucleotide P, 9% was phytate-like P, and 26% was nonhydrolysable P. This study indicates mild enzymatic hydrolysis is useful for quantifying labile (or hydrolyzable) forms of Po in dairy manure.

Last Modified: 9/10/2014
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