Kinetic parameters of plant species may differ among cultivars due to root morphology, root and plant age and nutrient status. Currently, limited information is available on the influence of foliar K on kinetic uptake parameters that describe K absorption by roots. The objective of this study was to evaluate the effects of foliar-applied K on kinetic uptake parameters of two cotton (Gossypium hirsutum L.) cultivars differing in maturity. The cotton cultivars, DP20 (early maturing) and DP90 (late maturing) were grown hydroponically in a growth chamber. At 21 days after planting (DAP), plants were transferred into K free nutrient solution and an equivalent of 10 kg KNO₃/ha was foliarly applied. An equivalent amount of water without K was applied to plants that were non-foliar controls. Kinetic parameters were calculated from nutrient depletions of low K solutions at 25 DAP. Root length, leaf area, total dry weight and K concentration in roots and shoots were determined. The approximate depletion rate for the first 210 minutes of rapid depletion were 0.24 and 0.31 µM/L per min respectively, for DP20 and DP90. The maximum influx (Imax) for both DP20 and DP90 nearly doubled under foliar treatment, suggesting that foliar K application stimulated K absorption by roots. The minimum concentration (Cmin) of K that could be absorbed by roots from solution was decreased by 55% for DP20 subjected to foliar K application, while there was no effect of foliar K application on Cmin of DP90. Foliar K increased the number of squares by 56 and 76% and the shoot tissue K increased by 14 and 26% respectively, for DP20 and DP90. Root length decreased by 13 and 17% respectively, for DP20 and DP90 subjected to foliar K. Our results suggest that, the addition of foliar K to cotton may stimulate uptake of K by roots. Thus, when K is limiting, foliar application of K may enhance K deficiencies. This observation might explain variable responses of cotton plant to foliar K under field conditions.