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.