Enhancing cropping of Navel orange by different agrochemicals foliar sprays

The present investigation was carried out during the two successive growing seasons of 2003 and 2004 on Washington Navel orange trees grown at El-Tarh region, El-Behera Governorate of Egypt. In order to study the effect of spraying the trees with different agrochemicals on vegetative growth, fruit drop, fruit retention and yield. Trees were divided into two groups , the first group was subjected to the foliage treatments when the fruit reached pea size (5 mm in diameter) and the second group at marble size (15 mm in diameter). Foliar sprays of urea or 2, 4-D alone at pea or marble stage significantly increased vegetative growth. In general, foliar sprays of 2, 4-D alone or with the different calcium compounds at pea or marble stage significantly increased fruit retention and decreased fruit drop after June drop. Final fruit retention was increased (23 - 69% over the control) and pre-harvest fruit drop was decreased (63 to 100% compared to the control) by spraying boric acid or 2, 4-D alone at the pea stage in both seasons. Spraying calcium superphosphate alone at the marble stage caused an increase in final fruit retention by 33 - 7% and a decrease in pre-harvest fruit drop by 61 -72% over the control in both seasons. [PUBLICATION ABSTRACT]