Effect of Soil Moisture Stress on Post Harvest Seed Physiology, Quality, and Chemical Composition of Soybean.

Seed quality is a critical facet in agriculture which determines the overall human and animal nutritional aspects. In order to produce high quality soybean seeds, it is essential that the crop is grown under optimal environment such as ideal soil moisture condition. The objective of this study was to investigate the effects of soil moisture stress conditions during reproductive stage on seed yield components, seed composition (protein, oil, fatty acids, and sugars), and seed minerals (N, P, K, Ca, Mg, Fe, Mn, Zn, Cu, and B) using two soybean cultivars grown under sunlit controlled environmental conditions. Plants grown in pots were subjected to five levels of soil moisture stresses, 100, 80, 60, 40, and 20% of daily evapotranspiration of the control at flowering and continued until maturity. Results of the analysis of variance showed the significant effects of cultivar, soil moisture stress, and their interactions on the studied seed quality traits. Seed weight of both the cultivars was negatively impacted by soil moisture stress. Seed protein, ash, palmitic, linoleic, sucrose, raffinose, stachyose, N, P, K, and Ca significantly decreased whereas oil, fiber, stearic, oleic, linolenic, Fe, Mg, Zn, Cu, and B increased in response to soil moisture deficiency. The relationship between seed protein and oil was negative while seed dry weight exhibited strong positive correlations between seed protein, sucrose, and N content. The changes in seed constituents could be due to changes in nutrient accumulation and partitioning in soybean seeds under the stress. The decrease of protein may be due to the decrease in both uptake and translocation of major nutrients such as N, P, and K under the moisture deficit. This information suggests the requirement of an adequate soil moisture condition during flowering and seed formation stages to obtain the beneficial effects of nutritional value of the soybean seeds.