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.
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