Soybean photosynthesis responses, yield, and grain quality affected by vermicompost and sulfur

Soybean (Glycine max L.) is considered as one of the major sources of oil and protein. In this study, the effects of vermicompost (VC) and sulfur (S) on soybean photosynthesis responses, yield, and grain quality were studied. To this end, a split-plot design field experiment based on randomized complete blocks with nine treatments and three replications were conducted in Aligudarz city, Lorestan province, Iran during 2017. The First factor included vermicompost treatments (0, 4, and 8 t h-1) as the main plot and the second factor included sulfur treatments (0, 250, and 500 kg h-1) as the sub plot. Results revealed that VC application significantly increased the stomatal conductance (gs), transpiration rate (E), net photosynthetic rate (PN), chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll a+b (Chl a+b), carotenoids (Car), grain yield (GY), grain oil content (GOC), and grain protein content (GPC) of soybean. Furthermore, S application (250 kg h-1) improved the important traits in comparison to the control treatments. A significant interaction was found between VC and S treatments, suggesting the combined application of VC and S may improve soybean physiological responses, yield, and grain quality in comparison with VC and S treatments alone.