Zinc oxide nanoparticles coated urea enhances nitrogen efficiency and zinc bioavailability in wheat in alkaline calcareous soils

Nitrogenous fertilizers have low efficiency in alkaline calcareous soils due to volatilization and denitrification. These losses cause economic environmental constraints. Coating of urea with nanoparticles (NPs) is an innovative strategy to improve crop yields by sustaining N availability. In the current study, zinc oxide nanoparticles (ZnO NPs) were synthesized by precipitation method and characterized for morphology and configuration, bond formation, and crystal assemblage using the X-ray diffraction and scanning electron microscope (SEM). The SEM results confirmed the size of ZnO NPs in the size range of 25 nm with cuboid shape. Urea fertilizer, coated with ZnO NPs, was applied to wheat crop in a pot trial. Two rates of ZnO NPs at 2.8 and 5.7 mg kg(-1) were selected to coat the commercial urea. A batch experiment was conducted to ensure the ammonium (NH4+) and nitrate (NO3-) ions release by amending the soil with ZnO NPs coated urea and comparing with non-amended soil. The gradual release of NH4+ was observed for 21 days from the ZnO NP-coated urea. In the second part of trial, seven different treatments of coated and uncoated urea were tested on wheat crop. Urea coated with ZnO nanoparticles at 5.7 mg kg(-1) improved all growth attributes and yields. The ZnO NP coated urea increased the N content shoot (1.90 g 100g(-1) DW) and potentially biofortified Zn content (47.86 mg kg(-1)) in wheat grain. The results are indicative of viability of a novel coating for commercial urea that will not only reduce N losses but also supplement Zn without additional cost of labor.