Effect of biochar application on growth, physiology and yield of soybean [Glycine max (L.) Merrill] under salt stress

A pot study was conducted to understand the effects of biochar on the growth, physiology, and yield of soybean under salt stress. Different biochar application rates (0, 5, 10, 15, and 20 tons ha-1) were applied to the soil before soybean seeds were sown into pots. Salinity treatment was applied at the flowering stage by irrigating soybean plants with 100 ml of NaCl (100 mM) once every 3 days. The treatment lasted 30 days, and a total of 1000 ml of NaCl solution was applied to each pot. Salinity significantly decreased the growth and yield of soybean. Biochar application at 10 tons ha-1 significantly increased the growth and yield components including root length, leaf area, plant fresh and dry weight, nodule number plant-1, Fv/Fm, leaf chlorophyll content, pod number plant-1, 100-seed weight, and grain yield whereas the leaves' relative ion leakage and water saturation deficit both decreased. Our findings suggested the application of 10 tons ha-1 biochar can promote an optimal growth, physiology and high yield of soybean.