Effect on Colwell soil-test P of storing air-dry soil samples at room temperature for up to seventeen years |
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| Authors: | MDA BOLLAND J DHALIWAL JW BOWDEN DG ALLEN |
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| Institution: | Western Australian Department of Agriculture, 3 Baron-Hay Court, South Perth, Western Australia 6151;Chemistry Centre of Western Australia, 125 Hay Street, East Perth, Western Australia 6004, Australia |
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| Abstract: | We wished to determine whether soil-test P was affected by storing air-dry soil samples at room temperature. The soil samples had been collected from field experiments and air-dried (<40°C) before measuring soil-test P (bicarbonate-extractable P). The samples were from field plots that had been treated with different applications of fertilizer P (superphosphate, rock phosphate) one or more years previously. Soil-test P was measured on two different sub samples of the same sample: either A, in the year the sample was collected; or B, after the sample had been stored at fluctuating room temperatures either from 2 to 8 years (four field experiments) or 17 years (59 field experiments). The room temperature ranged from 10 to 30°C, and averaged 17°C. The aim was to test whether soil-test P was systematically and consistently different between sub samples A and B. Differences between A and B were mostly small, and there were no consistent or systematic differences. For the Colwell soil test, applied to a range of south-western Australian soils, possible decreases in soil-test P due to continued reaction with the soil could not be detected using bicarbonate-extractable soil P, and storage of air-dry samples at room temperature did not significantly affect soil-test P measured up to 17 years later. We conclude that, provided fertilizer P has had time to react with soil in the field, no further changes in Colwell soil-test P occur during air-dry storage for up to 17 years at room temperature. |
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