Integrated use of seed priming and biochar improves salt tolerance in cowpea

Cowpea (Vigna unguiculata (L.) Walp.) is an important grain legume crop, mostly grown on marginal soils which hamper its productivity. Improvement of salt tolerance in cowpea is contemplated as a useful strategy to economically utilize salt-affected lands. This study was conducted to evaluate the role of seed priming and biochar application in improving salt stress tolerance in cowpea. Cowpea seeds primed with CaCl2, water, or not-primed were sown in pots having biochar or no biochar and grown under optimal (no stress) and salt stress (10 dS m-1) conditions. Salt stress hindered the seedling emergence, biomass production, and accelerated the Na+ toxicity and oxidative damage. Nevertheless, osmopriming improved the cowpea performance through early seedling emergence, increase in biomass production (80.8%), leaf area (20.1%), α-amylase activity (78.7%), chlorophyll content (48.8%), soluble sugars (49.5%) and reduced MDA content (27.3%) and total antioxidant activity (22.2%) under salt stress conditions. Biochar application improved the seedling growth and reduced the oxidative damage in cowpea plant under salt stress conditions. Osmopriming integrated with biochar application further enhanced the cowpea performance under optimal growth conditions and reduced the adverse effects of salinity stress. The combination of osmopriming and biochar application hastened the seedling emergence, seedling growth, α-amylase activity (78.7%), reduced the total antioxidant activity (12.5%) and Na accumulation (30%) under salt stress over respective control. In conclusion, biochar integrated with osmopriming improved the cowpea performance under salt stress condition through early and synchronized emergence, chlorophyll synthesis, sugar accumulation which reduced the oxidative damage and Na+ toxicity resulted in better seedling growth and biomass production.