Foliar application of biosynthesised zinc nanoparticles as a strategy for ferti-fortification by improving yield, zinc content and zinc use efficiency in amaranth

Deficiency in zinc is widely prevalent in developing countries. Ferti-fortification is one of the easiest and quickest options for improving the zinc content in food. Consumption of such food can provide zinc in adequate amounts to the individual. Nanotechnology is now envisioned as the future of agriculture owing to the immense advantages of nanoparticles over bulk materials. In this work, the effect of zinc nanoparticles (Nps) synthesized via biological route using moringa leaves extract was studied on seed germination, its growth parameters, zinc content and nutrient use efficiency in amaranth crop. Moringa leaves are rich in plant metabolites such as amino acids, alkaloids, flavonoids, sugars and fatty acids as confirmed by the UPLC-MS system analysis. The XRD studies show that the biosynthesized Nps were hexagonal crystals with an average size of 23.69 nm. The particle size as indicated by scanning electron microscopy was between 15 to 30 nm, and by DLS was 22.8 nm. Foliar application of 10 ppm biosynthesized zinc Nps, resulted in the highest plant height and fresh weight. Although, an increase in concentration of zinc applied through foliar route led to higher zinc content in the plant biomass, the nutrient use efficiency indices indicated that zinc Nps at 10 ppm concentration resulted in better nutrient recovery, improved yield and productivity with respect to the nutrient input. This reflects the advantage of biologically synthesized Nps over the bulk counterparts. These results show that the biologically synthesized Nps can be an attractive alternative to conventional fertilizers for nutrient biofortification and better crop yields.