Combined application of Eucalyptus-derived biochar and arbuscular mycorrhizal fungi improves growth, nutrient acquisition, antioxidant responses, and drought tolerance in Cicer arietinum

This study evaluated the individual and combined effects of Eucalyptus-derived biochar and arbuscular mycorrhizal fungi (AMF) on the growth, physiology, nutrient acquisition, and drought tolerance of Cicer arietinum. Plants were grown under normal and drought conditions and received biochar, AMF, or their combined application. Drought markedly reduced plant growth, photosynthetic performance, nutrient acquisition, nodulation, leghemoglobin content, and nitrate reductase activity. It also suppressed AMF colonisation, spore abundance, mycelial development, vesicle formation, arbuscule abundance, and root colonisation percentage. However, when applied together, biochar and AMF significantly alleviated these adverse effects. The combined treatment improved plant growth, chlorophyll production, net photosynthetic rate, relative water content, membrane stability, and antioxidant enzyme activity. Biochar also enhanced mycorrhizal establishment under drought, while treated plants maintained higher N and P concentrations than untreated drought-stressed plants. Treated plants showed greater nodule number and fresh weight, higher leghemoglobin content and nitrate reductase activity, and improved plant N status compared with untreated drought-stressed plants. Phosphorus and nitrogen uptake, which declined sharply under drought, were also substantially restored by the treatments. Overall, the combined biochar + AMF treatment produced the strongest responses across several measured traits under drought, including mycorrhizal colonisation, nutrient acquisition, nodulation, nitrate assimilation, photosynthetic performance, water relations, membrane stability, and antioxidant defence. These findings indicate that their combined application can improve drought tolerance in C. arietinum, although the present statistical analysis supports treatment-combination comparisons rather than formal inference of synergistic interactions.