Effect of Potassium and Glyphosate Foliar Applications On Mineral Concentrations in Soybean Cultivars.

Potassium (K) is an important nutrient for growth, yield, and seed quality. Previous studies showed that glyphosate (Gly) had negative effects on cation nutrients such as K, Ca, Zn, Fe. These effects may impact nutritional status of the cation nutrients in soybean seed. Therefore, additional studies are required. The objective of this study was to evaluate the concentration of cation nutrients such as K in soybean leaves as influenced by foliar application of K-Gly foliar applications. A greenhouse experiment was conducted using two cultivars (DK 4968 and Pioneer 95Y70). The treatments were foliar K alone, Gly alone, and K-Glyphosate combined. Non-treated soybean was used as a control. A single application of K (1.75%) as K₂SO₄ and Gly (0.75 ae/ha) was applied at V3 stage. Leaf samples were analyzed for mineral uptake one and three weeks after treatment (WAT). The concentration of K in leaves 3 WAT was higher in Pioneer 95Y70 in Gly treatment compared with control.  Also, the results showed there was a trend of increase in K, N, P, S in leaves in all treatments compared to the control, although this increase was not statistically significant. Leaf N increased in Pioneer 95Y70 in Gly and Gly-K treatments 1 WAT. However, leaf N concentration increased 3 WAT in K treatment in Pioneer 95Y70. Compared with the control, leaf Ca concentration decreased 3 WAT in DK 4968 in Gly and K-Gly treatment, but Ca concentration decreased 1 WAT in Pioneer 95Y70 in K-Gly treatment. Leaf Mn concentration decreased in Pioneer 95Y70 1 WAT in K-Gly treatment. Leaf Zn concentration significantly decreased in Pioneer 95Y70 3 WAT in Gly treatment. We conclude that foliar application of K and Gly on soybean may alter nutrient concentration in soybean leaves. Further studies are needed.