A study was conducted in Tubas district in a field located in Wadi Al-Fara’. The area is under irrigation and rich with ground water (Fara’ basin). Potatoe crop was selected as it is one of the most important irrigated crops in the area. Spunta cultivar was used. Two experiments were conducted. The first was conducted to determine the most suitable type of nitrogen source, and the second experiment was conducted to determine the optimal nitrogen fertilization for potatoes. It was found that the type and the amount of nitrogen fertilizer, added to potatoes plants, affected both crop quantity and quality. The vegetative dry weight was increased when nitrogen fertilizers were used. In addition, the use of both urea and ammonium sulfate increases potato yield. Mixing the organic acid fertilizer with ammonium sulfate or urea also increased the production insignificantly. It was found that increasing the amount of nitrogen increases the number of tubers, size, hardness and the density of the tuber. A quadratic significant relation was found between the yield and the amount of nitrogen fertilizer. A maximum yield of potato under the experimental conditions was obtained with 35kg/dunum nitrogen rate as ammonium sulfate. Yield at this rate was 4016kg/dunum. Nitrate residue in the root zone at the end of the season has increased significantly when more than 20kg nitrogen/dunum was added. When organic acid fertilizer was mixed with ammonium sulfate, the nitrate was increased in the soil profile and the salt leaching was also minimized.