Soybean Seed Composition as Affected by Foliar K and Applications and Cultivar Differences.

Potassium (K) is an essential nutrient for growth, yield, and seed quality for field crops.  The effect of foliar K application with and without glyphosate on seed composition has not been well studied. Therefore, further investigation in this area is needed. The objective of this study was to evaluate the effects of foliar K application alone, Gly alone, and Gly-K combined on seed composition in soybean. A non-treated soybean was used as control. Two glyphosate-resistant soybean cultivars (DK 4968 and Pioneer 95Y70) were grown in a greenhouse experiment. K (1.75% as K₂SO₄) and Glyphosate at the rate of 0.75 ae/ha were foliar applied at V3 stage. Mature seeds were harvested from all treatments to analyze for seed protein, oil, and fatty acids. The seeds were analyzed at USDA-ARS Delta States Research Center in Stoneville, MS using Near Infra-red (NIR) instrument. Although significant differences in seed protein and oil were not observed compared to control, percentage differences in these constituents could be important for seed quality. For example, protein percentage was higher than the control in all treatments in DK 4968 (the increase was 3.97% in the K, 6.94 % in Gly, and 3.51 % in the K+Gly combined treatments). An opposite trend was observed between protein and oil in DK 4968, especially in the glyphosate treatment where the decrease was 11.19% compared to the control. In Pioneer 95Y70, the decrease in oil was 2.74% in K-treatment and 2.3% in Gly-K combined treatments compared to control. Stearic fatty acid was significantly higher in Gly-K treatment compared to K treatment for DK 4968, suggesting that stearic acid percentage could be increased by K-Gly treatment. Also, stearic acid in Pioneer 95Y70 was significantly higher in Gly treatment (an increase of 8.33%) compared to control. An higher percentage increase in linolenic acid was observed in DK 4968 in K treatment (an increase of 24.49%) and K-Gly treatment (increase of 29.51%) compared to the control. We conclude that foliar application of K and Gly may affect seed composition constituents, but further research is needed.