Effects of Biochar on the Physicochemical Properties of Saline-Alkali Soil and the Growth and Metabolism of Melons

To mitigate the adverse effects of soil salinization on melon growth, this experiment utilized two melon cultivars (Cucumis melo L. cv. Tokyo Sweet Treasure and Xizhou Honey No. 17) under three biochar treatments (0%, 10%, and 20% of pot soil mass) and three salt solution irrigations (0, 75, 150 mmol/L). Physiological changes in melons and soil physicochemical properties were investigated at 7, 14, and 21 days post-treatment. Results demonstrated that biochar addition alleviated salt stress-induced inhibition of plant growth and soil degradation. Biochar promoted plant height, root elongation, and antioxidant enzyme activities, with maximum increases of 15.7% (SOD), 29.9% (POD), and 37.5% (CAT). Malondialdehyde (MDA) content decreased initially (up to 44.32%) and later increased. Moreover, optimal biochar ratios enhanced photosynthetic efficiency and significantly increased soil organic matter, while N, P, and K levels showed slight but upward trends. In conclusion, appropriate biochar application improves saline-alkali soil properties, enhances melon growth, and strengthens salt tolerance.