A field experiment was carried out at the Experimental Res. Farm of El-Kassasin Horticultural Research Station, Ismailia Governorate, (Around 30°.26^′ N 31°59^′ E) during two successive seasons; 2009/2010 and 2010/2011 to study the effects of applying two different nitrogen sources ammonium sulphate (AS) and ammonium nitrate (AN), at the same rate of 140 kg Nfed^-1, and their ratios on growth, yield marketable, quality and nutrient uptake of potato (Solanum tuberosum L.; CV. Nicola). A completely randomized design was established with 5 treatments, i.e., (AS) / (AN) ratios of 100/0, 0/100, 75/25, 50/50, 25/75 and.Each treatment had 3 replications. Representative samples were taken after 75 days and the yield was harvested after 120 days. Dry weights of tubers, at the harvest were increased significantly with all mixed nitrogen treatments as compared with single AS or AN.  The enhanced growth with mixed nitrogen was greatest at 25% (AS) Ammonium Sulphate + 75% (AN) Ammonium Nitrate. Such treatment produced maximum dry matter (24.20%), total yield (13.765 kg.fed^-1) and N,P and k uptake and marketable yield (86.6%) followed by the treatment having 50% AS +50% AN. Usage of 140 kg Nfed.^-1 applied as a mixture of 25% AS+75% AN achieved 17% and 11% increment of total yield compared to 100% of AS application and 100% AN, respectively. The study stressed on paying attention to selection of sources of N fertilizers and their ratios for potato plants grown in sandy soil.