Two field experiments on potato ( Solanum tuberosum, L.) crop were carried out at El-Qanater Horticultural Research station, Kalubiya, Governorate, Egypt for two successive seasons 2009 and 2010. The study concerned the use of different rates of potassium fertilization (72, 96 and 120 kg K 2O/fed.) under different irrigation schedulings (40, 60 and 80% from available water) on potato crop in alluvial soil. Generally, in most cases, the treatment of the medium or/and highest soil moisture level (60 and 80% from available water) gave the highest significant values for plant height, dry matter and K content of potato plant at 90 days from planting and potato yield tuber ton/fed N, P and K contents in tuber in addition to, total soluble solids and protein content in tuber as well as consumptive use. While the lowest one were recorded when the lowest soil moisture level (40% from 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 K 2O/fed. achieved the highest significant values of dry matter, content of N and K at 90 days from planting as well as N content in tuber. Whereas, the high values of tuber yield, protein content, water use efficiency and consumptive use were obtained when 120 kg K 2O/fed. was applied. In most cases, the high levels of potassium under 80% from available water gave highest significant values for all parameters under study in both seasons.
