This study was conducted at the experimental farm of Shandawel Research Station, Agricultural Research Center (ARC), Sohag Governorate, during the two seasons of 2016/2017 and 2017/2018 to study the effect potassium fertilization rates (25, 50, 75 and 100 Kg K/fed.) and foliar spraying with micronutrients (foliar spraying after 30 days, after 30 and 45 days, and after 30, 45 and 60 days from transplanting), on growth, yield, quality and storability of onion. Application of potassium at rate of 100 kg/fed appeared the highest values of plant height at 90 days in the second season, and at 120 days in both seasons. The highest means of bulb diameter were obtained by K fertilizer application at rate of 100 kg/fed, while the lowest means were recorded by application of 25 kg K, at 90 and 120 days in both seasons. Application of 100 kg K/fed. appeared the highest means of total yield/fed. and exportable yield/fed., while application of 25 kg K/fed. appeared the lowest means, in both seasons. Application of K fertilizer at rate of 100 kg/fed appeared the highest means of dry matter% and TSS%, while using of 25 kg K/fed. recorded the lowest means, in both seasons. Spraying three times with micro nutrients appeared the highest means of average bulb weight, while spraying one time recorded the lowest means, in both seasons. The highest means of dry matter% and TSS % were obtained by spraying three times with micro elements, while the lowest means were recorded by spraying one time. The best combination between the two factors were achieved by application of 100 kg K/fed. and spraying three times with micronutrients, this combination produced the highest values of total yield/fed. and exportable yield/fed., in both seasons.