Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2005
Publication Date: 1/1/2006
Citation: Baum, K., Pierzynski, G., Kleinman, P.J., Kovar, J.L., Maguire, R., Moore Jr, P.A., Zhang, T. Evaluating the Influence of Storage Time, Sample-handling Method, and Filter Paper on the Measurement of Water-Extractable Phosphorus in Animal Manures. Communications in Soil Science and Plant Analysis. 37(3-4):451-463. Interpretive Summary: Surface application of manures to agricultural soils can result in phosphorus runoff that accelerates freshwater eutrophication, the biological enrichment of surface waters that is widespread in the US. Recently, a growing body of research has pointed to water extractable phosphorus in land applied manures as a key indicator of dissolved phosphorus in runoff. This study evaluated various methodological factors affecting the determination of water extractable phosphorus in the laboratory, including sample holding time, sample handling procedure, and filtration method. Results of this study support the adoption of a standardized protocol for measuring water extractable P in manures that represents the appropriate balance between the ease of implementation and the strength of the correlation to P runoff concentrations.
Technical Abstract: Surface-applied manures create a potential phosphorus (P) runoff hazard, especially when unincorporated. In such cases, the concentration of water extractable P in the manure has been correlated to soluble P concentrations in runoff. This study evaluated the influence of holding time, sample handling procedure, and filtration method on measurement of the water extractable P content of manures in a 3 X 3 X 2 factorial arrangement of treatments. A two-way interaction between holding time and sample handling procedure occurred for most samples. Six samples had water extractable P concentrations that were less than or equal to dried and dried/ground treatments. Only one sample had higher water extractable P concentrations for fresh compared to dried and dried/ground treatments. When significant differences occurred as a result of the filtration method, results for Whatman 40 filters, with a larger pore size than 0.45'm nitrocellulose membranes, were usually higher. There was no significant difference in the coefficient of variation across sample handling procedures, suggesting that efforts to dry and/or grind samples were not needed. These results support the adoption of a standardized protocol for measuring water extractable P in manures that represents the appropriate balance between the ease of implementation and the strength of the correlation to P runoff concentrations.