Effects of Different Sources of Nitrogen Fertilizer On the Yield and Fruit Quality of Persian Lime Under Nubaria Conditions

A field study was conducted during the 2021 and 2022 seasons on 7‑year-old Persian lime trees grafted on Citrus volkameriana rootstock to investigate the effects of four nitrogen fertilization sources: ammonium sulphate (20.6%), urea (46.5%), granular ammonium nitrate (33.5%), and slow-release (40%) on yield and fruit quality. The results revealed that the yield of trees was significantly affected by different nitrogen forms. Compared with nitrogen applied through other sources, nitrogen applied through slow-release resulted in the highest yield and good fruit quality. The slow-release application ultimately resulted in the highest total average yield (4.05 t/feddan) and the lowest cost (561.73 LE/t fruit). The average cost of fertilizing granular ammonium nitrate, ammonium sulphate, and urea to produce one ton of Persian lime fruit was 975.32, 1106.01, and 607.85 LE/t, respectively. Urea-derived nitrogen had the greatest impact on fruit weight and increased fruit diameter and juice percentage, followed by slow-release nitrogen and granular ammonium nitrogen in both seasons. The nitrogen source also affected the colour, lightness, and hue angle of the Persian lime peel. In light of these results, it can be concluded that using N slow-release fertilization for Persian lime trees grown in sandy soil is a good choice for reducing the number of applications annually, reducing the production cost, and improving the efficiency of nitrogen used by the trees to obtain a high yield with good fruit quality.