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Title: LIGAND-BASED ENZYMATIC FRACTIONATION OF BIOACTIVE PHOSPHORUS IN DAIRY MANURE: FAST AND TIME-DEPENDENT PROCESSES

Author
item Dao, Thanh
item Reeves Iii, James
item ZHANG, H - OK STATE UNIVERSITY

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2004
Publication Date: 10/31/2004
Citation: Dao, T.H., Reeves III, J.B., Zhang, H. 2004. Ligand-based enzymatic fractionation of bioactive phosphorus in dairy manure: fast and time-dependent processes [abstract]. American Society of Agronomy. Annual Meeting Abstracts CDROM No. 5217.

Interpretive Summary: Summary.

Technical Abstract: Increased knowledge of phosphorus (P) chemistry in animal manure is important to understand P behavior in the environment. A study was conducted to develop a novel fractionation method for bioactive P forms that are present as water-soluble, complexed inorganic and organic P, and characterize fast reactive pools and time-dependent reactive pools in dairy manure. Readily water-extractable P (WEP) in 107 manure samples collected across the NE averaged 15.9 ± 14.8% of TP, thus varied considerably between farms. The conventional batch dilution method yielded notably higher dissolved P than those determined in undiluted manure liquid phase. The linear relationship between the two measures collapsed as the time of equilibration increased. Highly variable increase in 'apparent WEP' was attributed to concurrent time-dependent PO4 release following dilution and hydrolysis of organic P forms under favorable laboratory conditions. In addition, the entire set had a large pool of organic P that was hydrolyzed by exogenous phytases, releasing an additional 32.2 ± 15.6% of TP as PO4. Yet, another pool of complexed mineral phosphates was exchangeable with EDTA, which increased the mobilization of complexed P. The exchange yielded additional WEP and PHP that were coordinatively associated with Ca and Mg. Therefore, an increased understanding and quantitation of these P reserves must be accurately made as they ultimately add to the WEP fraction and become bioactive in time.