Soybean seed physiology, quality, and chemical composition under soil moisture stress

•Soybean seed protein and oil negatively correlated under drought stress.•Soil moisture stress increased the production of smaller and shriveled seeds.•Sucrose had a higher sensitivity towards moisture stress than other sugars.•Soil moisture stress affected mineral uptake.•Optimum soil moisture during seed formation improved soybean seed quality. Soybean seed quality is often determined by its constituents which are important to sustain overall nutritional aspects. The objective of this study was to investigate the effects of soil moisture stress during reproductive stage on seed quality and composition. Plants were subjected to five levels of soil moisture stresses at flowering, and yield and quality traits were examined at maturity. Seed protein, palmitic and linoleic acids, sucrose, raffinose, stachyose, N, P, K, and Ca significantly decreased whereas oil, stearic, oleic and linolenic acids, Fe, Mg, Zn, Cu, and B increased in response to soil moisture deficiency. The relationship between seed protein and oil was negatively correlated. The changes in seed constituents could be due to changes in nutrient accumulation and partitioning in soybean seeds under water stress. This information suggests the requirement of adequate soil moisture during flowering and seed formation stages to obtain the higher nutritional value of soybean seeds.