Abstract

Alternate bearing phenomenon is the tendency of some citrus varieties to produce a heavy crop in ON year followed by little crop in next year OFF year, in both seasons the crop fruit with poor quality (improper size, thick rind, and unattractive color) which had low economic value, consequently decrease producers profit. There are sensitive citrus varieties for alternate bearing like Mandarins and Tangerines, while grapefruit and pineapple orange have a moderate tendency; however, it is very week in Valencia orange trees. There are various internal and external factors effects on alternate bearing cycles include low C/N ratio, unbalanced hormones, and starvation of roots, abiotic stress conditions and availability of nutrition in the soil. There are negative effects for alternate bearing in sensitive varieties, such as broken the limbs in ON year, delayed fruit maturity, reduce fruit quality. Management of alternate bearing to increase crop in OFF year by using different practice including thinning fruit, hard pruning after OFF year, foliar application by chemical substances like Gibberellin acid and urea.