ARS | Publication request: DEVELOPING A WATER EXTRACTABLE PHOSPHORUS TEST FOR MANURES

Submitted to: Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 20, 2003
Publication Date: November 20, 2003
Citation: Kleinman, P.J.A., Wolf, A.M. 2003. Developing a water extractable phosphorus test for manures [Abstract]. Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting. Paper No. S08-kleinman686589-oral. 2003 CDROM.

Technical Abstract: Water extractable P (WEP) in manure has been correlated with phosphorus concentration in runoff from soils amended with manure. As a result, WEP is increasingly serving as an indicator of environmental phosphorus loss in site assessment indices. To develop a single, standard WEP test, this study examined methodological factors affecting WEP measurement in manure, and evaluated the reliability of applying such a test in commercial analytical laboratories. Results showed that, to serve as a consistent environmental indicator across multiple manures, a WEP test must fix the ratio of dry matter to solution as well as the extraction period. Narrow dry matter to solution ratios (1:10) were worse at predicting dissolved phosphorus in runoff than broad ratios (1:200) across a wide range of manures. Therefore, a ratio of 1:200 was selected for the WEP test. An inter-laboratory comparison of the proposed WEP test confirmed that the test could be replicated equally as well as other common manure tests (e.g., dry matter, total phosphorus). Thus, this study represents the final step in developing a universal WEP test for manures.