Synergetic effects of potassium and biochar on morphological, physiological, and biochemical attributes of maize crop grown under different levels of drought stress

Global climate change accelerates the challenges of agricultural drought spells, which are alarming for food security and can trigger food scarcity. Therefore, improving soil-water retention capability and crop drought resilience is becoming more important for sustainable agriculture. This study investigates the individual and combined effects of biochar and potassium on soil water retention, crop drought resilience, and related physio-biochemical mechanisms over a 50-day growth period in potted plants. Pine needle biochar (350 g/10 Kg of soil) was used during the soil preparation stage while potassium sulfate (100 mg/L) was applied as a foliar spray at the development (10 days) and vegetative stages (45 days) under three drought stress conditions: control (100% FC), mild (75% FC) and severe (40% FC). The results revealed that the combined application of biochar and potassium significantly increased morphological, physiological, and biochemical attributes of maize plants under drought stress, improving shoot fresh weight by 11%, 6%, and 5%, root fresh weight by 19%, 19%, and 23%, shoot length by 17%, 16%, and 19%, and root length by 21%, 30%, and 29% under control, mild, and severe drought stress conditions, respectively. Similarly, relative water contents (RWC) increased by 12%, 16%, and 20%, water potential (Ψ) increased by 26%, 22%, and 24%, osmotic potential (Ψs) increased by 100%, 59%, and 30%, and turgor potential (Ψp) increased by 28%, 35%, and 51% under combined treatment compared to control, mild, and severe drought stress. Additionally, biochar application with potassium foliar spray also improved membrane stability and integrity, cell wall loosening, membrane lipid peroxidation, and protein denaturing by decreasing electrolytic leakage by 35%, 28%, and 43%, proline by 30%, 27%, and 22%, hydrogen peroxidase by 47%, 45%, and 41%, and malondialdehyde contents by 24%, 20%, and 28% through activation of enzymatic (CAT, POD, SOD) and non-enzymatic (TSS, AsA, GSH) antioxidants. Furthermore, nutrient uptake was enhanced, with N increasing by 47%, 19%, and 45%, P by 64%, 82%, and 52%, and K by 24%, 42%, and 35% in shoots compared to normal, mild, and severe drought stress. These improvements mitigated cell dehydration, reduced transpiration inefficiency and delayed senescence, and ultimately supporting plant growth under drought stress. In conclusion, integrating biochar with potassium application effectively improves soil-water retention, alleviates oxidative stress and enhances drought tolerance in maize plants. This strategy can play a crucial role in sustainable agriculture by mitigating the adverse effects of drought stress and improving food security in drought-prone regions.