This study aimed to assess the impact of different sources, concentrations, and application methods of nitrogen on fruit set, yield, and the physical and chemical characteristics of Navel orange fruits. A field experiment was conducted during the 2020/2021 and 2021/2022 seasons on Navel orange trees onto sour orange rootstock at the Orchard of the Faculty of Agriculture, Menoufia University. The soil's texture is clay loam. The experiment followed a completely randomized block design. The results showed that the best N sources were the slow-release N fertilizer Enciabene, liquid ammonium nitrate, ammonium sulfate, and urea, in descending order. The combined application of Enciabene plus liquid ammonium nitrate gave satisfactory yield and fruit quality. Raising levels of Enciabene from 1.25 to 2.5 kg/tree had a slight effect on all the characters studied. Optimal yield and superior physical and chemical properties of Navel orange fruits were achieved by fertilizing the trees with 0.500 kg/tree of Enciabene in conjunction with 2 L/tree of liquid ammonium nitrate.