Integrated soil-foliar strategy using biochar and Zinc Oxide Nanoparticles reduces cadmium bioavailability and improves growth, antioxidant defense, and yield of Maize (Zea mays L.)

Abstract Aims Agricultural soils contaminated with cadmium (Cd) pose a serious threat to food safety and crop yield. Various conventional methods are employed to mitigate toxic effects; however, biochar amendments with ZnO NPs are particularly suitable for Cd remediation. Methods In this study, we examined the ability of biochar (BC) (1% and 2% w/w as a soil amendment) and zinc oxide nanoparticles (ZnO NPs; 250 and 500 ppm as a foliar application) to mitigate Cd-induced stress in maize (Zea mays L.). Results Exposure to Cd increased oxidative stress markers while significantly decreasing plant biomass, chlorophyll content, and photosynthetic efficiency. By increasing chlorophyll a/b ratios, improving growth performance, and increasing antioxidant enzyme activity, the application of ZnO NPs and BC, both separately and in combination, reduced oxidative damage. Interestingly, compared with Cd-stressed controls, the combination treatment significantly (p < 0.05) decreased Cd accumulation in maize roots, shoots, and grains. When ZnO NPs and BC were combined, they exhibited a synergistic effect that enhanced plant physiological tolerance to heavy metal stress and promoted redox equilibrium. The highest SOD, POD, and CAT values (98.8%, 99%, and 72%) were observed for T4 compared to the control. Conclusion Our findings suggest that BC and ZnO NP applications improve maize crop growth and yield and effectively mitigate the toxic effects of Cd.