Two field experiments were carried out at Kafer El-Zayat,. El-Gharbia Governorate, Middle Delta and allocated at 30-50' N Latitude, 30-49'E Longitude . during the two successive seasons of 2009/2010 and 2010/2011. The field is provided by tile drain network spaced at 20 m. with  1.2 m. depth, in order to study the effect of distances from drain line, potassium application and irrigation scheduling on yield of  potatoes. Experiments were conducted in a split- split- plot design. The study was concerned with the use of different rates of potassium fertilization (0, 72, 96 and 120 kg K₂ O/fed.) under different irrigation scheduling (40, 60 and 80 % of available water) Results showed that: Decreasing distance from drain line L/2 to L/4 to L/8 gave significant increase in potatoes yield. The study concerned the use of different rates of potassium fertilization (0,72,96 and 120 kg K₂O/fed.), under different irrigation scheduling (40, 60 and 80 % of available water)on potatoes crop in clay soil. Generally, in most cases, the treatment of the medium and highest soil moisture level (60 and 80 % of available water) gave the highest significant values, potatoes tuber, as well as, consumptive use. While the lowest one were recorded when the lowest soil moisture level (40% of available water) was applied.. Generally, all k rates gave the highest significant values for all parameters under study. The second level of potassium 96 kg K₂O / fed. achieved the highest significant values of tuber yield,. Whereas, the high values of  water productivity and consumptive use were obtained when 120 kg K₂O/fed. and 40% available water were applied. In most cases, were high levels of potassium under 80 % of available water gave the highest significant values for all parameters under study in both seasons.