ZINC DIFFUSION AND SELF-DIFFUSION COEFFICIENT IN ALKALINE SOILS AS AFFECTED BY SOIL PROPERTIES AND ZINC CARRIER

The apparent diffusion coefficients, D(p)/b+theta, of Zn and ZnEDTA were linear functions of added Zn, and were related to the adsorption and fixation capacities of soils rather than their pH. Lower apparent diffusion coefficient values were found in an Haplustoll soil that had higher clay and humus contents inspite of its lower pH. At comparable rates of added Zn, the apparent diffusion of ZnEDTA was 930-1010 (Bakyria), 700-1330 (Dirab), and 730-1880 (Baha) times that of Zn in the soils. The adsorbed Zn per cm3 of soil/Zn per cm3 of the equilibrium solution at the water content existing in the diffusion experiment approximated the capacity factor and was determined by extrapolation. The self-diffusion coefficient of Zn in Baha soil (5 x 10(-7) cm2sec-1) of higher clay and water content was higher than in Bakyria or Dirab soil (2 x 10(-7) cm2sec-1). These values were similar to the self-diffusion coefficient of P in soils of similar texture at similar water content.