EFFECT OF SPRAYING NAVEL ORANGE TREES WITH SOME ANTIOXIDANTS ON GROWTH AND PRODUCTIVITY

Abstract

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 grafted on sour orange rootstock and grown in a private orange orchard in Qalyubia 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 (250, 500 and 1000 ppm) plus control treatment spraying with tap water so the experiment included ten treatments. Selected trees were sprayed three times (at the beginning of the spring growth cycle in March, after fruit setting in May and 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 or 1000 ppm citric acid or 1000 ppm folic acid. Regarding to yield, results pointed out that the foliar spraying with 500 ppm salicylic acid or 500 ppm citric acid and or 250 ppm folic acid gave the highest values of yield. Navel orange trees spraying with 500 ppm salicylic acid or 250 ppm citric acid or 250 ppm folic acid gave the highest values of physical and chemical fruit properties. Regarding to total protein percentage and total phenolic compounds, results pointed out that the foliar spraying with 500 ppm folic acid gave the highest values of total protein percentage whereas 1000 ppm folic acid gave the highest values of total phenolic compounds. In respect to nutrients content, the highest values of macronutrients were obtained by all folic acid levels whereas 250 ppm citric acid gave the highest value of Mg percentage. The foliar spraying by 1000 ppm salicylic acid gave the highest values of micronutrients. Therefore, using 500 ppm salicylic acid may be recommended from economical point of view and as good treatment for enhancing Navel orange growth, yield, fruit quality and nutritional status especially under old citrus orchards.