The impact of moisture deficit stress on the yield response of cotton (Gossypium hirsutum L.) to foliar-applied K is not well understood. Studies were conducted in Arkansas from1999 through 2002 at three field locations to evaluate the effect of irrigation and soil-applied K on the yield response of cotton to foliar-applied K. Eight treatments consisting of soil-applied K and no soil K with or without foliar-applied K, plus irrigation or no-irrigation were arranged in a split-split plot design with five to six replications. For most site-years, lint yield was not enhanced by foliar K where soil K applications were made according to current University of Arkansas recommendations. Response to soil-applied K varied with initial soil K fertility level. Across site-years, lint yield responded 40% of the time to soil-applied K under irrigated conditions whereas yield did not respond under non-irrigated conditions. Variation in rainfall among the growing seasons moderated the response of lint yield and yield components to irrigation. The data suggest that a yield response to soil-applied K may be observed more frequently in irrigated cotton grown in the mid-south when compared to non-irrigated cotton. Lint yields typically were not enhanced by foliar-applied K applications on soils where preplant, Melich 3 K levels ranged from 270-376 kg K ha-1, irrespective of irrigation. Further research is needed to determine the interactive effects of water-deficit stress and soil- and foliar-applied K on the yield of cotton grown where soil residual K levels range from low to medium.
