GA3 AND ZINC SPRAYS FOR IMPROVING YIELD AND FRUIT QUALITY OF ‘WASHINGTON NAVEL ORANGE AND TREE GROWTH UNDER SANDY SOIL CONDITIONS

2 Abstract: This study was carried out during two successive seasons (2005 and 2006) on ten years old Washington na vel orange trees ( Citrus sinensis L. Osbeck) bud ded on Volkamer l emon ( C. volkamerina 3 L.) rootstock, grown in sandy soil in a private orchard at Sadat district, Minufiya Governorate, Egypt. GA at 10 or 20 ppm was sprayed twice (beginning of April and be ginning of June) also,chelated zinc at 0.4% was sp rayed three times (m id February, beginning of A pril and beginning of Ju ne). T he obtained results revealed that most treatments esp ecially t hose includ ed zinc sprays improved leaf N, K and Zn c ontents. 3 However d ata proved that G A sprays a t 2 0 ppm were more effective than that at 10 ppm in term of f ruit set, fruit retention and yield as fruit number or weight (Kg) per tree. Spraying 0.4 % chelated zinc al one 3 or wi th G A especially at 20 ppm significantly increased fruit set, fru it retention, decreased fruit drop and subsequently improved the y ield as well as the p hysical and chemical fruit characteristics. So, spraying 3 0.4% chelated zi nc at mid Februa ry followed by spraying 0.4% chelated zinc + 2 o pp m G A twice at (beginning of April and beginning of June) seems to be the promising treatment for increasing productivity of low y ield Washington navel orange trees grown unde r s andy soil condition.