Optimum fruit size is one of the most important parameters determining the profitability of citrus production to acquire high marketing value. The study was conducted on Valencia orange trees (Citrus sinensis L.) budded on sour orange rootstock (Citrus aurantium). Trees were planted at 5x5 m spacing (168 trees/feddan) growing in sandy soil under flood irrigation at a private orchard in Wadi Elmolaak area at Ismailia, Governorate, Egypt. An experiment was conducted on mature trees of Valencia orange to study the effect of different concentrations of manganese spread at different times on the incidence of chlorosis, yield, and mineral contents. Trees sprayed with chelated Mn at 0.3% in March, June, and September. Treated trees had less percentage of chlorosis than non-sprayed trees. The same treatments also have the largest yield. Nitrogen, potassium, and iron contents were decreased as the rate of Mn sprays increased. Nitrogen content was increased as the number of applications increased.