Effect of Spraying with some Antioxidants on Growth, Yield, Fruit Quality and Nutritional Status of Navel Orange Trees

This study was carried out through two consecutive seasons 2016 and 2017 to investigate the effect of spraying with some antioxidants on vegetative growth, yield, fruit quality and nutritional status of twelve years old Navel orange trees on sour orange rootstock grown in a private orange orchard in Qalubia Governorate, Egypt cultivated in a silty clay loam soil. This experiment involved three antioxidant materials named (salicylic acid, citric acid and folic acid) and each one spraying by three levels of each of with (250, 500 and 1000 ppm) from each salicylic, citric and folic acid plus control treatment so the experiment included ten treatments. Selected trees were spraying three times (at the beginning of the growth cycle in March, just after fruit setting in May and just after June drop in July) by aqueous solution of salicylic acid, citric acid and folic acid until the point of runoff. The highest values of vegetative growth were obtained by spraying 500 ppm salicylic acid, 1000 ppm citric acid and 500 ppm folic acid. Regarding to yield, results pointed out that the foliar spraying with 500 ppm salicylic acid, 500 ppm citric acid and 250 ppm folic acid gave the highest values of yield. Treatments 500 ppm salicylic acid, 250 ppm citric acid and 250 ppm folic acid gave the highest values of physical and chemical fruit properties. In respect to nutrients content, the highest values of macronutrients were obtained by spraying 250 ppm folic acid, while that spraying 1000 ppm salicylic acid and 250 ppm folic acid gave the highest values of micronutrients. Therefore, using treatments 500 ppm salicylic acid, 500 ppm citric acid and 250 ppm folic acid may be recommended from economical point of view and as good treatments for enhancing Navel orange growth, yield, fruit quality and nutritional status especially under old citrus orchards.