This investigation was carried out during seasons of 2006 and 2007 on Golden Japanese plum trees to study the effect of four potassium fertilizer sources (potassen, liquid potassium, potassium nitrate and Coda-PK) and control treatment sprayed at bud burst, after fruit set and one month after fruit set. Results revealed that all treatments significantly increased fruit set, yield, fruit weight, fruit size, fruit length, fruit diameter, total sugar and K (%) in both seasons, while they decreased fruit drop (%) compared with the control. Coda-PK treatment gave the highest yield compared to other treatments in both seasons followed by liquid potassium, potassium nitrate and potassen in adescending order. The tested treatments enhanced total carbohydrates and leaf macro-elements content. Storage studies on "Golden Japanese" plum fruits showed the high ability of fruits for keeping quality at 5°c for about one month without changing in aroma or taste.