Potassium (K) is the most influencing plant nutrient in cotton production due to its positive effects on the yield and fiber quality of cotton. However, due to the scorching prices of K fertilizers, the farmers around the globe seldom include K in cotton nutrition program. A variety of strategies are devised for low-K-input sustainable cotton production, including the identification of K-use-efficient genotypes and the integrated use of inorganic and organic sources of K. This monograph focuses upon K use efficiency of cotton genotypes, in a series of hydroponics, pot and field experiments, and how it is affected by inorganic and organic K fertilizers. Various factors affecting