Comparative Performance of Nano-ZnO and Nano-Fe₂O₃ Fertilizers on Wheat Yield and Biofortification

Micronutrient deficiencies, particularly zinc (Zn) and iron (Fe), significantly limit wheat productivity and grain nutritional quality in calcareous soils, contributing to hidden hunger in populations heavily dependent on cereal-based diets. This study aimed to evaluate the effectiveness of nano-based micronutrient fertilizers compared to conventional sources in improving wheat growth, yield, biofortification, and nutrient use efficiency under semi-arid conditions. A field experiment was conducted in the Sharazoor Plain, Halabja , using a randomized complete block design with four treatments: control, conventional conventional zinc sulfate (ZnSO₄) + iron sulfate (FeSO₄), zinc oxide nanoparticles (ZnO), and combined zinc oxide nanoparticles + iron oxide nanoparticles (ZnO + Fe₂O₃). The soil composition consisted of clay loam with a mild alkalinity (pH 7.6) and contained a total calcium carbonate level of 19.8%. It exhibited a deficiency in readily available Zn and Fe, as indicated by diethylenetriaminepentaacetic acid extractable concentrations of Fe and Zn measuring 0.39 mg kg⁻¹ and 0.63 mg kg⁻¹, respectively. Nanofertilizer treatments significantly enhanced plant growth parameters, with the combined nano-ZnO + nano-Fe₂O₃ treatment producing the highest plant height (93.67 cm), tiller density (413.33 m⁻²), and chlorophyll index (SPAD 50.93). Yield components were markedly improved, resulting in a maximum grain yield of 5.53 Mg ha⁻¹, representing a 39% increase over the control. Grain quality was also enhanced, with protein content increasing to 13.30%, while Zn and Fe concentrations reached 48.83 and 51.17 mg kg⁻¹, respectively. Overall, nano-based zinc and iron fertilizers, particularly the combined ZnO + Fe₂O₃ treatment, significantly improved wheat growth, yield, grain protein, and micronutrient concentrations, highlighting their potential for sustainable biofortification and enhanced nutrient use efficiency in micronutrient-deficient soils.