Efficacy of modified biochar for enhancing maize photosynthesis and yield under various irrigation regimes

Maize (Zea mays L.), a globally significant cereal of the Poaceae family, plays a pivotal role in food and feed security. However, its productivity is increasingly threatened by climate-induced drought stress and low organic matter content of soil, particularly in arid and semi-arid regions. This study aimed to investigate the interactive effects of organically modified biochar supplementation on soil physicochemical properties, plant physiological responses, and yield performance of maize under varying irrigation regimes. The experiment was conducted under field conditions using Acacia nilotica-derived biochar and modified with vermicompost and perlite at the Botanical Garden, University of the Punjab, Lahore. The biochar was applied in the soil at two application rates (5 and 10-tons ha^-1), in combination with five irrigation regimes (100%, 80%, 70%, 60%, and 50% of crop evapotranspiration). Results revealed substantial improvements in soil quality and plant performance with biochar application. Specifically, the 10 tons ha^-1 biochar treatment significantly increased soil pH (by 6%), organic matter (by 24%), and saturation percentage (by 47.8%) compared to untreated soil. The Brunauer-Emmett-Teller (BET) surface area, and pore volume also improved with biochar application. Photosynthetic rate rose by 43.2%, while transpiration rate and total chlorophyll content increased by 9-folds and 50.5%, respectively. Yield-related parameters exhibited marked enhancement, with cob length increased by 68.3%, and thousand-seed weight by 121% under 10 tons ha^-1 biochar and full irrigation (100% ETc) compared to control. This study concludes that organically modified biochar serves as a promising soil amendment to improve soil fertility, enhance physiological resilience, and optimize maize yield under water-limited conditions. The findings provide a scalable strategy for sustainable crop production and resource-efficient agriculture under climate change scenarios.