Tuesday, 8 November 2005
13

The Effect of Extraction Vessel Type in Mehlich III, DI, Bray, and Olsen Phosphorus Soil Analysis.

Daniel Ebeling1, Joel Davis1, and Angela Ebeling2. (1) Wisconsin Lutheran College, 8800 W. Bluemound Rd., Milwaukee, WI 53226, (2) University of Wisconsin, 9723 W Wisconsin Avenue, Wauwatosa, WI 53226

Several phosphorus extraction methods exist for the determination of P in soils. When these extractions are employed, they will often be carried out in either Erlenmeyer flasks or plastic conical tubes. The choice of extraction vessel can have a significant impact of the P results. In order to determine the extent of the variation due to differing vessels, Mehlich III, deionized water, Bray Kurtz, and Olsen P extractions were repeatedly performed on two different soils. For each trial, three extraction variations were compared: shaking in Erlenmeyer flasks, shaking in conical tubes, and shaking in conical tubes followed by centrifugation. Each of the samples were then passed through a 0.45 micron filter and analyzed spectrophotometrically by the standard ascorbic acid method. The general trend in each of the extractions was for the Erlenmeyer flasks to lead to lower soil test P values with higher standard deviations.

Back to Phosphorus Chemistry in Soils: I. P Availability
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