Previous research on the Northern Texas Blackland soils has failed to show a clear or consistent cotton response to soil-applied or foliar-applied potassium fertilizer. The objectives of this study were 1) to quantify the effect of soil-applied potassium fertilizer on the quantity and quality of cotton lint yield at various row spacings; 2) to determine the ability of post-flowering, foliar-applied potassium fertilizer to improve cotton yield; and 3) to determine how K fertilization affects K distribution within the plant. Research was conducted at the Texas Agricultural Experiment Station Research farm at Prosper, Texas during the 2000 and 2001 growing season. During both years, 0, 40, and 80 lbs/acre of KCl was applied to 20-, 30-, and 40-inch row spacing cotton crops. Foliar applied KNO₃-K was applied biweekly starting shortly after first flowering. Growing seasons varied greatly from one year to the next with high temperature and drought during the 2000 growing season followed by adequate moisture and lower temperatures for the 2001 growing season. Twenty- and 30-in cotton row spacings did not respond to soil- or foliar-applied K during either growing season, but there was some evidence that lint yields for 40-in cotton rows responded positively to soil-applied K fertilization. The response was clearest for the droughty 2000 growing season. Analysis of cotton tissue from the 2001 growing season showed that soil-applied K also increased K concentrations in the stem tissue of 40-in row cotton. There was no clear cotton response to foliar applications of KNO₃.