Two field experiments were carried out at Mallawi requirements research station El-Minia Governorate, Egypt; Water Management Research Institute -National Water Research Center during 2012 and 2013 seasons.The aim of this investigation is to evaluate the effect of the different irrigation regimes and potassium fertilization rates on crop coefficient of potato. Also it evaluate and compare the potential evapotranspiration (ET p ) with actual water requirement under El-Minia Governorate conditions. The experiment included five treatments of irrigation regimes (A) and four treatments of potassium fertilization (B) with three replicates so that the experiment was arranged in a split plot design. The irrigation regime treatments were treationial irrigation (the farmers practes, 100%, 90%, 80% and 70% of field capcity). Potassium rates was applied in a form of potassium sulphate (48%K 2 O) at rate 200 kg/fed. (b 1 ), 100 kg K 2 O/fed. + potasine (Biofertilizer) at rate 6 liters/fed (b 2 ), 100 kg/fed. + potasine (Biofertilizer) at rat 6 liters/fed. + potassium foliar (36% K 2 O) at rate 2 liters/fed. (b 3 ) and Potassium (biofertilizer) at rate 6 liters/fed (b 4 ).These results indicated that the first irrigation treatment where plants irrigated with conventinal irrigation had the highest value of actual consumptive use (daily and seasonal). This was due to the decrease in the value of tension moisture of the first treatment which led to increasing the water actual consumptive use. While, the fifth irrigation treatment for plants irrigated until 70% of field capacity had the lowest value of actual consumptive use (daily and seasonal). The application of Potassium fertilization caused a slight decrease in daily, monthly and seasonal actual evapotranspiration(ET a ), in both seasons. Modified Penman and modified Blaney & Criddle gave high average values for potential evapotranspiration (ET p ) (63.24 and 56.50 cm/season) while radation method and pan method gave less average values (53.99 and 49.11 cm/season) for the two studied seasons respectively. The actual values of evapotranspiration were less than those computed by climatological equations. This is due to the estimated factors in these equations.The average values of potential evapotranspiration (ET p ) for the two studied seasons, by modified Blaney & Criddle and radation method were the nearest values to general average (+1.41 and -3.09% respectively). While, the farthest values to general average were obtained by modified Penman and Pan method (+13.52 and -11.85% respectively). Kc average were 0.76, 0.72, 0.71, 0.70 and 0.68 for A 1 , A 2 , A 3 , A 4 and A 5 under all subtreatments respectively. Modified Blaney & Criddle was the nearest to the actual consumptive use.Therefore, recommended for calculating the potential evapotranspiration using modified Blaney & Criddle or radiation method for potato plants which grow under El-Minia conditions and other corresponding conditions.

Two field experiments were carried out at Mallawy Water Requirements Research station-El Minia, Governorate; Egypt Water Management Research Institute-National Water Research Center during 2012 and 2013seasons. The present research was carried out to study the effect of water stress and planting methods on yield, saving water and quality for Potato crop (Solanum tuberosum L). A split plot design with three replicates was conducted. The main plots were assigned to five irrigation treatments traditional irrigation (the farmers practices), 100%, 90%, 80% and 70% of field capacity for potato crop and the sub plots into two planting methods (furrow and beds). The treatments of irrigation were distributed at random in the main plots. While planting methods treatments were distributed at random in the sub-plots. Results indicat that irrigation regime significantly affected total yield in both seasons, where values of total yield/fed. were increased as water stress increased until 80% of field capacity then decreased with 70% of field capacity in both seasons. Also planting method was significantly affected this character in both seasons. The highest yield of potato was obtained with planting in beds and saving water about 14.42% compare to planting in furrow in both seasons. The obtained results in present study show that when the best method was used (irrigated potato until 80% of field capacity and planting in beds A 4 b 2) the irrigation water is saved more than the normal planting in furrow (common method in region) by about 29.72% in both seasons. This treatment was the most superior treatments (from view point water and production) on this character. Starch content values were significantly increased as water stress was decreased where the highest values of starch content (based on dry weight) were obtained when plants irrigated by conventional irrigation (72.820 and 74.400) in the first and second seasons, respectively. Planting method significantly affected this character in both seasons, where the highest values were obtained from plants which planting in beds in both seasons. The interactions between the studied factors significantly affected strach content in both seasons. Irrigation regime significantly affected the protein content in both seasons, where the highest value was obtained from plants which irrigated with conventional irrigation (6.958 and 7.035%) in the first and second seasoins, repectively. Irrigation regime significantly affected total soluble solids percentage (TSS) and dry matter content in both seasons , where they were increased with increasing water stress in both seasons, and the maximum values of (TSS) and dry matter content were recorded when plants grown at the lowest level of water supply i.e. irrigation at 70% depletion of available water. Irrigation regime was significantly affected the specific gravity (g/cm 3) of potato in both seasons, where the specific gravity was increased significantly as watrer stress was increased. Planting methods significantly affected on this character...