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This article in SSSAJ

  1. Vol. 41 No. 3, p. 537-540
    Received: Aug 23, 1976
    Accepted: Jan 25, 1977

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Observed and Predicted Rates of Phosphorus Diffusion in Soils of Varying Bulk Density and Water Content1

  1. G. S. Hira and
  2. N. T. Singh2



The self-diffusion coefficient of phosphorus (D) was measured at bulk densities of 1.25, 1.45, 1.60 and 1.75 g/cm3 and at three levels of soil water content in Choa sandy loam and Haibowal silty clay loam. The tortuosity factor was calculated from the self-diffusion coefficient of 36Cl. Appropriate values of the adsorption isotherm and the tortuosity factor were used to predict P diffusion coefficient in both soils.

The tortuosity factor increased with increase in soil bulk density and increase in water content from 7 to 18% in the Choa soil and 14 to 25% in the Haibowal soil. As bulk density increased from 1.25 to 1.60 g/cm3, the observed diffusion coefficient values averaged over all water contents, increased from 0.05 × 10−10 to 0.31 × 10−10 and 2.13 × 10−10 to 5.07 × 10−10 cm2/sec in Choa and Haibowal soils, respectively. Further increase in bulk density to 1.75 g/cm3 decreased the diffusion coefficient. At high bulk density changes in water content affected the self-diffusion coefficient of P in both soils to a greater extent than at low bulk density. The phosphate ion-soil particle interaction was minimum at a soil bulk density of 1.60 g/cm3.

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