الفهرس 
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Abstract
four field experiments were conducted at the experimental farm faculty of agriculture mansura university, egypt during 2007 and 2008 seasons. a randomized complete block design for each experiment irrigation treatment in four replicates was used. the objectives of this investigation was aimed to study the effect of irrigation treatments (on the basis of soil water depletion) i.e. from field capacity treatments, combination between mineral nitrogen and organic fertilizers, and their interactions on growth, yield and its components, quality, storability as well as chemical analysis of potato (solanum tuberosum l.) cv. spunta. • the main results of this investigation could be summarized as follows: • from obtained results it could be concluded that maximum total tuber yield (ton/fed), marketable tuber yield/fed, and protein content in tubers (%) were produced by irrigation tensiometer reading at 26cb (2233.413 m3 water/fed) i.e. 54.2 % from field capacity and fertilization with 60% mineral nitrogen fertilizer (99 kg n/fed) plus 40 % organic poultry manure (66 kg n/fed) in both seasons. • moreover, the highest values of water use efficiency (kg/m3) was recorded with irrigation at 34 cb i.e. 45.8 % from field capacity and fertilization with 20% mineral n fertilizer plus 80 % poultry manure in the first seasons and fertilization with 60% mineral nitrogen fertilizer (99 kg n/fed) plus 40 % poultry manure (66 kg n/fed) in the second seasons. • moreover, minimum total losses percentage, nitrate and nitrite concentration (ppm) in tuber were produced by irrigation at 34cb (1437.876 m3 water/fed) i.e. 45.8 % from field capacity as well as application of 100 % organic poultry manure (165 kg n/fed) in both seasons under the environmental of dakahlia governorate.