Effect of nitrogen fertilization on yield, fruit quality and leaf composition of navel oranges [Egypt]
1988
Moustafa, A.A. (Cairo Univ., Fayoum (Egypt). Faculty of Agriculture) | El-Aidy, A.A.
This investigation was carried out for two seasons on twenty-five Navel orange trees grown at Ebshway district, El-Fayoum governorate. The experiment included four levels of nitrogen fertilization, namely; 1250, 1875, 2500 and 3125 g. ammonium nitrate/ tree/ year, in addition to, the unfertilized tree (control). The fertilizer was added twice (February and june) during the growing season. Nitrogen application increased fruitsize and weight, as well as number of fruit per tree and consequenty increased the crop. The high nitrogen level induced the largest and heaviest fruits, in addition to, the highest fruit number and weight per tree. Meanwhile, fruit juice TSS was increased and acidity decreased as nitrogen application increased. The treatment of 2500 g. N./ tree/ year showed the highest values with respect to TSS/ acid ratio. It gave the best index of fruit quality and correspondingly the fruit taste was sweet. Vitamin C content was, also, raised as nitrogen application increased up to 2500 g. N./ tree, while this response was reversed after that. Generally, there were gradual and significant increments in N content and slight declines in P and K content of leaves as nitrogen fertilization increased. Meantime, increasing the rate of nitrogen application raised slightly leaf Ca, Mg and Mn content, but, the rate of increment remained relatively constant when nitrogen fertilization exceeded 1875 g. N./ tree/ year. However, the influence of applied nitrogen on leaf Zn content was not consistent. leaf photosynthetic pigments content was influenced by nitrogen fertilization. There were actual increments in chlorophyll A and B, as well as, slight increases in carotenoids as nitrogen application increased.
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