Green-synthesized ZnO nanoparticles as sustainable bionanofertilizer for Corchorus olitorius growth and zinc biofortification

Zinc deficiency affects over 50% of agricultural soils globally and is a key constraint on crop yield and nutritional quality in tropical regions. Conventional zinc fertilizers such as ZnSO4 have limited nutrient use efficiency (< 5%) due to soil fixation and leaching. This paper examined the effectiveness of neem-mediated zinc oxide nanoparticles (NMZ) with neem leaf extract (NLe) as a sustainable bionanofertilizer for Corchorus olitorius plants (COp). Characteristic NMZ absorption peaks were verified with a UV-Visible spectrophotometer, and a crystal structure of hexagonal wurtzite with an average crystallite size of 16.8 nm was revealed by the X-ray diffraction analysis. Fourier Transform Infrared Spectra demonstrated the capping of phytochemicals in NLe. Dynamic Light Scattering results revealed progressive size reduction of highly monodisperse particles with a polydispersity index less than 0.3. Brunauer Emmet Teller analysis showed a relatively higher surface area of smaller particles. Results also revealed that the plant height of COp grew by 28% relative to the control, growing to 18.5 cm at week 7. Leaf count grew by 19%, and the chlorophyll content reached its peak of 31.8 ± 0.5 mg/g fresh weight (FW) of leaves. Soil analyses after harvests showed that NMZ treatments had maintained an optimal pH (6.15–6.26) and significantly enhanced the quantity of available zinc. Plant tissue analysis confirmed enhanced zinc uptake, with shoot zinc content reaching 0.032% in 0.05 M treated plants compared to 0.012% in controls. The results affirm that NMZ is a promising and sustainable complement to conventional zinc nutrition strategies, warranting further field-scale validation.