Two field experiments were carried out at Sids Agricultural Research station, Beni-Suef Governorate in 2009 and 2010 seasons, to study the effect of the potassium sulfate and potassium humate on Egyptian cotton cultivar, Giza 80 (G. barbadense L.). The aim was to investigate the effect of two concentrations of soil potassium humate (80 %) with rate of 4 and 6 kg / fed. and foliar application of potassium humate with 2 and 3 g / L. sprayed at pinhead square, start of flowering and peak of flowering stages, on growth, leaf nutrient contents, earliness, seed cotton yield and yield components. The obtained results could be summarized as follows: Foliar application of potassium humate produced the highest values of leaf N, K, Ca, Fe, Zn, Mn and Cu ppm, contents as compared with the other treatments. All treatments led to significant increase of leaf macro and micronutrients contents compared with the control treatment, but values of leaf P % and Mg % content were not significantly increased. All treatments significant increase of leaves content of chlorophyll a, b, (a + b) and carotenoids. The highest seed cotton yield / fed. and yield components showed significant increase in the application of soil potassium humate (4 kg / fed. + spraying cotton plants potassium humate 2 g / L.). The application of potassium humate significantly increased number of fruiting branches, number of open bolls/plant, boll weight, seed cotton yield / fed., oil % and protein % in seeds of cotton as compared with the control treatment in both seasons. Various treatments had insignificant effects on lint %, earliness % and fiber quality in both seasons. Key words: potassium sulfate, potassium humate, Growth, leaf nutrient, yield and yield components, oil, protein.