Diffusion of Zinc in Soils as a Function of Applied Zinc, Phosphorus, and Soil pH

Abstract Self‐diffusion coefficients, D , of 65 Zn were determined in two Texas soils. In the Norwood loam, a calcareous soil of pH 8.2, the effect of applied P and Zn on diffusion coefficients was studied. As the applied P was raised from 0 to 240 ppm, the D value obtained at 0 ppm Zn decreased significantly from 11.73 × 10 ‐11 to 8.57 × 10 ‐11 cm 2 /sec; at 40 ppm Zn, the D value decreased significantly from 28.51 × 10 ‐11 to 16.33 × 10 ‐11 cm 2 /sec. Zinc diffusion doubled as the applied Zn was increased from 0 to 40 ppm at all levels of applied P. In the Nacogdoches sandy loam, a soil initially of pH 6 but subsequently raised to pH 7.2 and 7.9 by liming, there was little difference between the D values obtained at pH 7.2 and 7.9. When the applied Zn was increased from 0 to 20 ppm, the D value increased from 5.35 × 10 ‐11 to 7.83 × 10 ‐11 cm 2 /sec at pH 7.2 and from 3.97 × 10 ‐11 to 6.26 × 10 ‐11 cm 2 /sec at pH 7.9. However, D values obtained at pH 6 were much larger than those obtained at pH 7.2 and 7.9. As the Zn level was raised from 0 to 20 ppm at pH 6, the D value increased from 19.90 × 10 ‐11 to 19.53 × 10 ‐9 cm 2 /sec. It appears from this study that the effect of Zn and pH on diffusion of Zn is greater than that of applied P.