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.

Two field experiments were carried out during 2013/2014 and 2014/2015 seasons to study the effect of organic fertilization (farmyard manure "FYM" at the rate of 20 t/fed and humic acid "HA" at the rate of 20 kg/fed), NPK fertilization (50 % of the recommended doses i.e. 40 kg N + 20 kg P 2 O 5 + 40 K 2 O/fed and 100 % of the recommended doses i.e. 80 kg N + 40 kg P 2 O 5 + 80 K 2 O/fed) and foliar spraying with some biostimulants (without, foliar spraying with Stemo at rate of 0.5 ml/liter water, potassium salicylate at rate of 2.0 ml/liter water, Super-grow at rate of 1.5 ml/liter water and mixture of Stemo at rate of 0.25 ml/liter water + K. Sal at rate of 1.00 ml/liter water + Super-grow at rate of 0.75 ml/liter water) as well as their interaction on growth, yield and its components and chemical composition of pea Master B cultivar. The experiment was carried out in a stripsplit plot design with three replications. The obtained results could be summarized as follows:-The maximum means of all studied characters were recorded by humic acid (HA) at the rate of 20 kg/fed, while the minimum values were resulted from using farmyard manure (FYM) at the rate of 20 t/fed in both seasons.-Increasing NPK fertilization levels from 50 % of the recommended doses (40 kg N + 20 kg P 2 O 5 + 40 K 2 O/fed) to 100 % (80 kg N + 40 kg P 2 O 5 + 80 K 2 O/fed) was accompanied with significant increase in all studied characters.-Foliar spraying with mixture exceeded the other treatments with some biostimulants and resulted in the highest means of all studied parameters in both seasons. It could be recommended that organic fertilizing pea plants with humic acid at the rate of 20 kg/fed and mineral fertilizing with 80 kg N + 40 kg P 2 O 5 + 80 K 2 O/fed in addition to foliar spraying three times with the mixture of biostimulants i.e. Stemo at rate of 0.25 ml/liter water + K. Sal at rate of 1.00 ml/liter water + Super-grow at rate of 0.75 ml/liter water in order to maximizing pea growth, yield and quality.