Hibiscus cannabinus Biochar Enhances Crop Health and Soil Biochemical Functioning in Barley under Drought Stress

Drought stress is a critical constraint to crop health, productivity, and soil functional stability in arid and semi-arid agroecosystems. This study evaluated the potential of Hibiscus cannabinus-derived biochar to enhance physiological resilience and soil biochemical functioning in barley (Hordeum vulgare L., cv. ‘TJ-70’) under water deficit conditions imposed at tillering and grain-filling stages. A controlled pot experiment was conducted with biochar incorporated at 30 and 40 g kg⁻¹ soil prior to sowing. Water deficit markedly impaired crop health by reducing biomass accumulation, chlorophyll content, photosynthetic rate, and grain yield, while elevating oxidative stress and suppressing soil enzymatic activities and microbial-associated biochemical indicators. Biochar amendment significantly alleviated drought-induced damage by improving photosynthetic performance, chlorophyll retention, and antioxidant defense systems, including superoxide dismutase, catalase, and peroxidase activities, thereby minimizing oxidative injury. In parallel, biochar application enhanced soil biochemical attributes, reflecting improved microbial functionality and soil health under moisture-limited conditions. The higher application rate (40 g kg⁻¹) consistently produced greater improvements in both plant physiological performance and soil biochemical stability. Overall, these findings demonstrate that H. cannabinus-derived biochar effectively enhances crop health by integrating plant stress tolerance with soil functional restoration, highlighting its potential as a sustainable management strategy for drought-prone cropping systems.