Growth, physiological, and yield response of soybean (Glycine max L.) to soil–vermicompost ratios under different water regimes

Water stress is one of the serious challenges affecting crop growth and yield. Due to decreased precipitation and higher evaporation resulting from climate change, water stress will continue to become more frequent and severe in many areas. The study was conducted to evaluate the growth, physiological, and yield response of soybean to vermicompost ratios under different water application levels. The treatments were 100% soil, 90:10, 80:20, and 70:30 soil-to-vermicompost ratios combined with water application levels of 90%, 60%, and 30% of field capacities. Results showed that vermicompost ratio, water application levels, and their interaction significantly affected the growth, physiological, and yield parameters. The 20% and 30% vermicompost ratios under optimum water application level (90% field capacity) were found superior in improving the growth, physiological, and yield parameters. Under optimum level, the 30% vermicompost ratio increased leaf area plant per plant by 15.8%, chlorophyll b (Chl_b) by 60.8%, and total chlorophyll (Chl_T) by 37.6% compared to the control. Under severe stress, the 20% and 30% vermicompost ratios increased Chl_b by 26.8% compared to the control. Stomatal conductance was increased by 39% under optimum water application due to the 20% vermicompost ratio compared to the control. Under optimum water application, the 30% vermicompost ratio increased the grain yield plant per plant by 161% compared to the control. The findings indicate that mixing vermicompost at different ratios can mitigate the negative effects of moderate water stress. Under severe stress, no significant improvement was observed in the parameters studied except for Chl_b and Chl_T.