Widespread production of glyphosate-resistant soybean (Glycine max) and economic situations affecting production has increased interest in foliar “weed and feed” soybean management systems.  Research was conducted in 2004 and 2005 in Northeast and Southeast Missouri to determine soybean yield response and salt injury from foliar-applied potassium (K) fertilizer sources and rates of application and the impact of K fertilizer source and rate of application on weed control when tank mixed with glyphosate at 0.84 kg ae ha^-1.  Potassium thiosulfate (0-0-25-17) (N-P-K-S), chloride (0-0-62),  phosphate (3-18-18), and 5-0-20-13 were applied at 2.7, 10.8, and 21.5 kg K₂0 ha^-1.  Soybean injury was less than 10% 22 days after treatment.  Soybean injury and weed control was affected by foliar K application rate in the presence of glyphosate.  No grain yield increases over the weed-free control was observed at either site in 2004.