Iron Biofortification of Wheat Grains by Foliar Application of Nano Zero-valent Iron (nZVI) and Other Iron Sources with Urea

Abstract

Iron (Fe) deficiency caused by inadequate dietary intake is a global nutritional problem in humans, especially in developing countries. Biofortification of wheat with Fe is, therefore, an important challenge and a high-priority research task. In this study, a field experiment was conducted to examine the effects of foliar Fe treatments with or without urea on the biofortification of wheat grains. For this purpose, foliar-applied different Fe sources (FeSO₄, Fe-EDDHA and nZVI, at the dose of 0.2% Fe) with and without urea at the stages of stem elongation, booting and flowering stages of wheat crops were investigated for two different sites in field conditions. Before and after foliar treatments; whole plant, old leaf, flag leaf, spike and grain samples were collected respectively depending on plant growth period. nZVI (nano zero-valent iron) was synthesized under laboratory conditions and was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and elemental dispersive X-ray (EDX) analysis. Total Fe and N concentrations were determined in these samples, and yield and protein contents were also determined in grains. In addition to this, active Fe concentration and SPAD value were determined in fresh plant samples. According to the results, all Fe sources in the first site and FeSO₄ + urea and nZVI + urea in the second site significantly increased grain Fe concentration as compared to control. SPAD value of the leaves generally increased with Fe fertilizers; active Fe concentrations in all foliar Fe-applied plants were found to be higher than those of control treatments. Foliar Fe fertilization had no significant effect on grain yield and protein contents in both sites. Foliar application of FeSO₄ with urea increased wheat grain Fe concentration to a critical value of 50 mg kg⁻¹ and it was the most effective treatment for Fe biofortification of wheat grain. On the other hand, nano fertilizers may also be an alternative potential fertilizer for Fe nutrition and Fe biofortification in plants in the future.