Iodine uptake by plants is thought to be affected by iodine form, soil pH and organic matter content. We investigated time-dependent water-soluble iodine in soil and its uptake by maize in limed and humic acid amended soil fertilized with iodide and iodate. A laboratory incubation and a wire-house pot experiment were conducted. In both, iodine was applied at 3 mg kg⁻ 1 soil, while lime (CaCO₃) and humic acid were each applied at 3 g kg⁻ 1 soil. Water-soluble iodine (WSI) in iodide-fertilized soil stabilized within one month, except in limed soil where a slight decline occurred after the second month. In contrast, iodate-fertilized soil showed 2–6 times higher WSI than iodide, gradually decreasing from 938 to 562 µg kg⁻ 1 over three months. Humic acid did not affect WSI in iodide-treated soils but reduced it by 24–48% under iodate fertilization. Limed soils fertilized with iodide exhibited a temporary WSI increase, whereas iodate consistently maintained 1.5-fold higher WSI. Iodine application did not reduce grain yield or biomass, while liming caused a significant reduction. Compared to iodide, iodate fertilization resulted in 5–7 times higher iodine concentrations in leaves and 5–11 times higher in stalks. In limed soil, iodate further boosted iodine concentration in leaves and stalks. The grain concentration achieved (103–176 µg kg⁻ 1 ) could fulfill 27–47% of the recommended dietary allowance. Iodate fertilization, especially with liming, enhanced iodine availability and uptake in maize tissues, achieving grain concentrations that can significantly contribute to dietary iodine intake in deficient regions.
Naeem et al. (Sat,) studied this question.