Effects of salinity, imazethapyr, and chlorimuron application on soybean growth and yield

Soybean is an important crop worldwide. Soybean cultivars differ in their sensitivity to soil salinity and herbicide damage. In these experiments, we examined the impact of salinization and herbicide (imazethapyr and chlorimuron) application on the growth and yield of two soybean cultivars, Essex and Manokin. Experiments were conducted in small pots in the greenhouse, in outdoor sand cultures, and in drip-irrigated field plots. Plants were irrigated with non-saline water or saline water (electrical conductivity, EC = 7 dS/m) with a composition typical of those in areas affected by sulfate-dominated salinity. Morphological changes resulted from herbicide application, including leaf elongation and formation of large shoots at the cotyledonary node. Herbicide treatment significantly reduced main stem height, number of nodes on the main stem, and stem diameter relative to the controls (not treated with herbicide); responses from the two herbicides were not significantly different. Salinity had a significant effect on seed weight: yield for Essex (a Cl accumulator) was significantly higher when irrigated with fresh water, while yield for Manokin (a Cl excluder) was significantly larger for plants irrigated with saline water. Yield for Essex was greater than that for Manokin when the plants were irrigated with fresh water; but at the higher irrigation water salinity (7 dS/m), Manokin produced significantly greater yield than Essex. Although herbicide application significantly impacted several growth variables, herbicide treatment had no significant impact on yield.