Observed and Predicted Rates of Phosphorus Diffusion in Soils of Varying Bulk Density and Water Content
1977
Hira, G. S. | Singh, N. T.
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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