Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/11/2005
Publication Date: 6/16/2006
Citation: He, Z., Toor, G.S., Honeycutt, C.W., Sims, J.T. 2006. An enzymatic hydrolysis approach for characterizing labile phosphorus forms in dairy manure under mild assay conditions. Bioresource Technology. 97:1660-1668. Interpretive Summary: Increased understanding of manure phosphorus (P) chemistry is needed for developing best P management practices to optimize recycling of manure P while minimizing the adverse environmental effects of animal manure application. Whereas manure P chemistry can be investigated by various approaches, characterizing labile organic P is a challenge due to their susceptibility to hydrolysis. In this study, we characterized dairy manure organic P by enzymatic hydrolysis at pH 5.0. About 75% of total manure P in the fresh manure was characterized by this approach. Data obtained in this study indicate that mild enzymatic hydrolysis was useful for quantifying labile (or hydrolyzable) organic P forms in dairy manure. Quantifying labile P forms by this approach may advance our ability to manage manure P in an environmentally responsible manner.
Technical Abstract: Characterizing labile P forms in animal manure is a challenge due to their susceptibility to hydrolysis. In this study, we enzymatically characterized P forms in dairy feces under mild assay conditions. Fresh dairy feces collected from a representative dairy farm in New York was separated into soluble and residual components. The hydrolyzable organic P was then characterized by enzymatic hydrolysis to simple monoester P, polynucleotide P, phytate-like P, and nonhydrolyzable P. In the water extracts, 77% was inorganic P, 11% hydrolyzable organic P and 12% non-hydrolyzable P. In the residual resuspension, the distribution of characterized P was 25%spontaneous labile P, 32% simple monoester P, 7% polynucleotide P, 9% phytate-like P, and 26% nonhydrolyzable P. Autoclaving released residual P in a level similar to that observed with spontaneous hydrolysis over 54 h. This suggests that autoclaving sped the release of spontaneously hydrolyzable organic P in animal manure and can be used as a simple and rapid way to identify the most labile organic P. Quantifying labile P forms by this approach may advance our ability to manage manure P in an environmentally responsible manner.