Cotton crop is the main stay of Pakistan’s economy. It occupies a central position in the national economy. Potassium is an essential nutrient for normal plant growth. The timing of any foliar spray is critical to the optimum efficiency of the foliar treatment. It is important to recognize that it is generally cheaper to supply K from soil-applied potash than it is to make supplemental foliar-application. Correcting K deficiency in fast-fruiting cotton cultivars requires information on growth response to available soil K, soil K2O rates, and supplemental foliar. This project investigated the effect of foliar and soil application of K2SO4 fertilizer on the growth, yield and fiber properties of cotton variety NIAB and evaluated the effect of foliar and soil application of K on soil and plant content.