Response of Populus deltoides to amended soil under water deficit condition

Soil amendment with water-retentive and stress-mitigating materials, including biochar and superabsorbent polymers, has been shown to improve soil moisture availability and enhance plant tolerance to water deficit. The present study aimed to mitigate the adverse effects of drought stress in poplar by amending soil with biochar (BC), superabsorbent polymer (SAP) and silicon (Si), applied individually and in combination, and to evaluate their effects on morpho-physiological and biochemical responses under cyclic drought conditions on Poplar cuttings ( Populus deltoides ) which were grown in plastic pots under polyhouse conditions. Plant growth was significantly improved under well-watered conditions in amended soils, with biochar exhibiting the strongest individual effect. The combined treatment of biochar, superabsorbent polymer, and silicon (D_BC1_SAP1_Si1) under drought stress resulted in the greatest enhancement of growth, biomass accumulation, leaf area, and gas exchange attributes. The lowest EL leakage (72.67) and the highest MSI (34.33) was found in D_BC1_SAP1_Si1 treatment. The stress index based on ratio of MDA and RWC across various treatments revealed the lowest value in across all BC treatment (< 0.25) as compared to without BC. It was also observed that biochar combination outperforms in all combination of treatment. Soil nutrient availability remained largely unaffected by treatments, except for potassium and sulphur, whereas soil pH, electrical conductivity, and organic carbon content showed significant variation among treatments. The combined use of biochar, superabsorbent polymer, and silicon synergistically mitigated drought stress and offers a viable strategy for poplar plantations in water-scarce environments where agroforestry practices are important.