A PHOSPHATE SORPTION INDEX FOR SOILS |
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Authors: | B W BACHE E G WILLIAMS |
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Institution: | Department of Soil Fertility, Macaulay Institute for Soil Research, Aberdeen |
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Abstract: | Phosphate sorption isotherms covering a wide concentration range (10?6 to 5 × 10?3m phosphate) were determined for 42 soil samples at 20 °C by a standardized technique. The slope of a plot of the sorption, x, against the logarithm of the equilibrium solution phosphate concentration, log c, measured at c= 10?4M, proved a suitable reference index to characterize the phosphate sorbing properties of the soils. Several single-point methods were tested by statistical correlation against this reference index. Of these, the sorption, x, from one addition of 150 mg P/100 g soil gave r= 0.951, but r= 0.974 when the equilibrium concentration was also taken into account in the quotient x/log c. This quotient is therefore suggested as a simple yet adequate way of indicating a fundamental soil property, its phosphate sorption isotherm. |
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