Diffusion of Iron and Iron Chelates in Soil

The importance of diffusion in moving Fe to plant roots was estimated by theoretical calculations. In plant studies chelates increased the diffusion and uptake of Fe by increasing the concentration gradient of diffusible Fe to sorghum roots ( Sorghum vulgare ). Uptake of Fe increased linearly with the concentration of Fe in solution. Self‐diffusion coefficients of Fe and Fe chelates were determined in both aqueous media and soil. In aqueous media, the diffusion coefficients were 6.2 × 10 ‐6 cm 2 sec ‐1 for Fe, 5.4 × 10 ‐6 cm 2 sec ‐1 for FeEDDHA, 4.2 × 10 ‐6 cm 2 sec ‐1 for FeDTPA, and 3.9 × 10 ‐6 cm 2 sec ‐1 for FeEDTA. In soil, a correction factor was used to adjust the apparent porous system self‐diffusion coefficients. The corrected diffusion coefficients in soil were 1.5 × 10 ‐7 cm 2 sec ‐1 for Fe and 1.85 × 10 ‐7 cm 2 sec ‐1 for FeEDDHA.