Integration of Seed Priming and Biochar Application Improves Drought Tolerance in Cowpea

Cowpea is a highly nutritious grain legume crop, cultivated mostly in a semi-arid environment and frequently confronts sporadic dry periods during different stages of plant growth, which drastically reduce its productivity. The current study was enacted to evaluate the biochar application and seed priming induced drought tolerance in cowpea. The seeds of cowpea were primed with CaCl2 (1% solution), water (hydropriming) (positive control), and dry seeds (absolute control), sown in pots with and without mango wood biochar. The water holding capacity (WHC) in well-watered and drought-stressed pots was maintained at 70% and 35%, respectively. Drought stress caused a delay in germination and reduced plant growth. Osmopriming enhanced seed germination, seedling growth, dry biomass production, chlorophyll contents, leaf area, soluble sugar contents, CO2 assimilation, water use efficiency (WUE), and leaf K+ concentration and inhibited the oxidative damage in cowpea under drought. The addition of biochar was effectively recuperated by the drought-induced growth reduction in cowpea. Osmopriming + biochar application increased the biomass production (115%), alpha-amylase activity (81%), chlorophyll contents (76%), total soluble sugars (60%), WUE (95%), leaf osmotic potential (25%), and leaf sap K + concentration (25%), and decreased the MDA content and total antioxidant activity by 34 and 28%, respectively, than non-primed control without biochar application under drought. Osmopriming supplemented with biochar amendment augmented the performance of cowpea under normal and water-deficit conditions through synchronized seedling emergence and better growth, chlorophyll synthesis, CO2 assimilation, osmolyte accumulation, and nutrient uptake with minimal oxidative damage, which lead to better cowpea performance in drought stress condition. Osmopriming and biochar application may prove effective in improving cowpea performance under changing climate.