Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2005
Publication Date: 10/1/2006
Citation: Kleinman, P.J.A., Sharpley, A.N., Wolf, A.M., Beegle, D.B., Elliott, H.A., Weld, J.L., Brandt, R. 2006. Developing an Environmental Manure Test for the Phosphorus Index. Communications in Soil Science and Plant Analysis. 37(15-20):2137-2155. Interpretive Summary: The advent of phosphorus-based manure management for water quality protection has focused attention on practices that reduce the availability of phosphorus in manure to runoff water. Phosphorus site assessment indices must therefore account for these new methods, as well as for differences in manures that are applied to agricultural soils. A series of studies was conducted to develop a water extractable phosphorus test for manures that accurately and consistently predicts phosphorus in runoff when manures are land applied. Steps were then taken to adapt the test to a commercial analytical laboratory setting. A survey of 140 manures submitted to one commercial laboratory revealed that water extractable P in livestock manures differ significant between livestock categories, with swine > poultry and dairy cattle > beef cattle. Such results support the creation of Phosphorus Source Coefficients in phosphorus site assessment indices. Ultimately, Phosphorus Source Coefficients for individual manures will be derived directly from this test.
Technical Abstract: The widespread implementation of the Phosphorus (P) Index has focused attention on environmental manure tests that can be used to estimate the relative availability of P in manure to runoff water. This paper describes the development and use of a water extractable P (WEP) test to differentiate manures within the context of the P Index. Water extractable P of surface applied manure was shown to be strongly correlated to dissolved P concentrations in runoff from agricultural soils. Water extractable P tests that fix the total solids to deionized water ratio and involve extraction times of 30 to 120 minutes provide the best prediction of dissolved P in runoff across a wide range of manures. Consistent measurement of manure WEP can be achieved with manure holding times of up to 22 days (4o C), acidified extract holding times of 18 days and solid separation by either centrifugation or paper filtration. Replicability of WEP tests is comparable to other manure tests (e.g., total P), verified by within lab and inter-lab evaluations. A survey of 140 livestock manures revealed significant differences in mean WEP of different livestock manures, with swine > poultry (turkey, broiler and layer chickens) and dairy cattle > beef cattle. Such results support the creation of P Source Coefficients to modify the source component of the P Index. Ultimately, P Source Coefficients for individual manures will be derived directly from the WEP test.