Two field experiments were conducted during 2013 and 2014 winter seasons to study the effect of foliar spray with potassium nitrate, potassium silicate, potassium chloride, and monopotassium phosphate at the rates 1000 ppm and 2000 ppm on growth, yield parameters and some biochemical constituents of potato plant (Solanum tuberosum L.). Two samples were taken after 65 days from sowing and at harvest. At the 1st sample date, plant length, shoot fresh weight, shoot dry weight, total chlorophyll reading, total nitrogen and proteins, P, K, Mg, Fe, Mn, and Zn concentrations (in potato leaves) were determined. At the 2nd sample date (harvesting stage), tubers number per plant, tubers weight/plant, yield/plant, and yield/Fadden were recorded. The higher rate of potassium silicate and potassium nitrate were more effective than the rest treatments on enhancing the vegetative growth parameters and yield components. In general, all potassium treatments have a strong stimulating effect on mineral nutrients (N, P, K, Mg, Zn, Mn, and Fe) and protein concentration of potato leaves in both seasons.