In light of the widespread reports of K deficiency and responses to foliar fertilization on sites with adequate soil K levels, a series of studies were initiated to reevaluate current soil test ratings and recommendations, and to examine the benefits and risks of foliar K applications for cotton on relatively high-yielding sites. Eight sites with high yield potentials were selected. Six of the sites were equipped with irrigation. At three of the sites, only soil applications were evaluated, while both soil and foliar applications were evaluated at the remaining five sites. Results indicate current soil test calibrations appear to be working very well for prediction of K needs of cotton at the yield levels attained in these tests (700 to over 1300 lbs lint per acre). Only on sandy sites receiving prolonged rainfall or heavy irrigation and no topdress applications did recommendations appear to break down. This is an expected result. For sites with high leaching potential, the use of sidedress K applications is strongly recommended to prevent early season losses. One site clearly demonstrated that soil applications can meet all the potassium needs. But when deficiencies do appear during the fruiting period, foliar applications are effective in improving yields.