Response of Potato Plants to Sources and Rates of Potassium Fertilizer

Two field experiments were carried out at a Private Farm in Meet Habib Village, Gharbia Governorate, during Winter seasons of 2015/2016 and 2016/2017 to determine the influence of potassium fertilizers levels, foliar application treatments and interactions on growth, yield and some chemical constituents in both leaves and tubers of potato cv. Spunta. Mineral fertilizing with 75 % of the recommended doses recorded the highest values of vegetative growth characters, total marketable tubers yield/fed, total soluble solids percentage (TSS) and vitamin-C content in fresh potato in both seasons. While, the highest values of total carbohydrates and starch percentages, nitrite and nitrate concentrations in fresh potato tubers were obtained from fertilizing with 100 % of the recommended doses in both seasons. Total sugars percentage in fresh potato tubers had reverse trend of all studied characters in both seasons. Foliar spraying potato plants four times with commercial fertilizer (MegaPot as a source of nitrogen, potassium and sulphur) at the rate of 1.5 g/liter water exceeded other foliar application treatments and produced the highest values of vegetative growth characters, yield and quality parameters of tubers, except total sugars percentage, nitrite and nitrate concentrations in fresh potato tubers. It can be concluded that mineral fertilizing potato by 75 % of the recommended dose as a soil application in addition to foliar spraying four times with commercial fertilizer MegaPot (as a source of nitrogen, potassium and sulphur) at the rate of 1.5 g/liter water in each spraying is the best to obtain high growth, yield, chemical composition and quality of potato Spunta cultivar.