F. Rivas, M. Juan, V.Almela, M. Agusti
Departamento de Producción Vegetal, Cátedra de Citricultura, Universidad Politécnica de Valencia.
Departamento de Citricultura, Instituto Valenciano de Investigaciones Agrarias. Valencia, Spain
Department of Fruit Tree Sciences. Israel
The effects of girdling performed at various dates were evaluated during two consecutive years in high- and lowbearing commercial orchards of ‘Fortune’ mandarin and ‘Clausellina’ Satsuma mandarin. The time-dependent response was evaluated through fruitlet abscission, final fruit-set and yield as related to carbohydrate contents in developing fruitlets. A few days after treatment, girdling increased the soluble sugars content (SSC) in fruitlets, reduced the daily fruit drop, and thereby diminished abscission. Application of girdling to low-bearing ‘Fortune’ mandarin orchards was most effective 15 d before anthesis (DBA) and 35 d after anthesis (DAA). It increased yield by 125%. In high-bearing orchards, the best results were achieved by girdling 35 DAA, which increased yield by 28%.
In both orchards, the effect of girdling declined gradually from 35 DAA to the end of fruit drop. SSC values were found to be positively correlated with fruit-set at 25 DAA, but this tendency was reversed by 50 DAA. This study showed that the effects of girdling are time-dependent, and that yield can be improved in cultivars of different parthenocarpic ability.