Interactive Effects of Rice Husk Biochar and Zinc Oxide Nanoparticles on Physio-biochemical Traits, and Yield of Buckwheat (Fagopyrum esculentum) under Salinity Stress

Abstract

Salinity stress negatively affects the physiological and biochemical processes of plants, leading to reduced yields. This study addresses the knowledge gap regarding effective strategies to mitigate salinity-induced damage and enhance productivity in buckwheat. We hypothesized that zinc oxide nanoparticles (ZnO NPs) and rice husk biochar could improve salinity tolerance in buckwheat by modulating its physiological and biochemical responses. To test this, common buckwheat plants were grown under irrigation with well-watered (0 mM salinity) and moderate saline water (75 mM salinity) following a completely randomized design (CRD) with three replications. Results showed that the application of 50 g/kg rice husk biochar and 200 ppm ZnO NPs, either separately or in combination, significantly enhanced the yield and improved key physiological and biochemical traits, including relative water content, photosynthetic rate, stomatal conductance, chlorophyll content, and antioxidant activity. The combination of ZnO NPs and rice husk biochar led to improvements in the plants’ relative water content, photosynthetic rate, chlorophyll levels, membrane stability index (MSI), proline, antioxidant activity (DPPH), and seed yield by 18.32, 15.29, 40.18, 14.54, 38.56, 6.87, and 40.78%, respectively, compared to untreated salinity plants. Moreover, this treatment reduced oxidative stress indicators such as hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) by 25.56 and 35.0%, respectively. These results show that ZnO NPs, when combined with rice husk biochar, significantly improve salinity tolerance in common buckwheat, providing a viable strategy to increase crop yields in saline environments. In view of climate change, this study emphasizes the potential of combining biochar with nanomaterials for sustainable agricultural practices.