Mitigating Salt Stress in Cotton through Biochar Amendments: Effects on growth, Oxidative Stress, and Microbial Activity

Abstract Purpose This study aimed to evaluate the effectiveness of tobacco-derived biochar in mitigating salt stress in cotton ( Gossypium hirsutum L.) by assessing its impact on physiological growth parameters, oxidative stress indicators, and soil microbial activity under greenhouse conditions. Methods A greenhouse experiment was conducted using saline and non-saline soils, with biochar applied at three doses (8, 16, and 24 g kg − 1 soil) in a randomized complete block design with three replicates. Measurements included plant growth traits (root and shoot length, biomass, SPAD values, stomatal conductance), oxidative stress markers (H₂O₂, MDA, proline), antioxidant enzyme activities (APX, POD, CAT), and soil enzyme activities (catalase, urease, dehydrogenase). Results Under saline conditions, biochar application at 24 g kg − 1 significantly improved cotton root and shoot biomass by 30% and 25%, respectively. SPAD values and stomatal conductance increased, while H₂O₂ and MDA levels decreased. Antioxidant enzyme activities and microbial enzyme levels were enhanced by up to 40%, demonstrating the positive role of biochar in alleviating salt-induced oxidative stress and improving soil health. Conclusion Biochar, particularly at higher doses, enhances cotton resilience to salinity stress by improving physiological performance and microbial activity. These results highlight the potential of biochar as a sustainable soil amendment for saline agriculture.