Effect of branch girdling on the alternate bearing, yield, and fruit quality of grapefruit (Citrus paradisi Macf.)

Objective: The objective of this research was to evaluate the effect of girdling branches, application of gibberellic acid (GA3), and foliar urea on the alternating yield and quality of grapefruit (Citrus paradisi Macf) fruits. Design/methodology/approach: The experiment was carried out on trees during abundant harvest (“on” year) and trees with low harvest (“off” year). Foliar applications of GA3 and foliar urea were performed with a manual sprayer at a rate of 7 L tree-1 of solution. Branch girdling (5.0 mm wide) was performed on two-thirds of the secondary branches using a circular-edged knife to avoid damaging the xylem. The experimental design was completely randomized, with 24 factorial arrangements with 16 treatments and 3 repetitions. Each experimental unit was a tree to evaluate fruit yield and quality at the experiment's conclusion. Results: Branch girdling increased the diameter, the number of fruits, the yield, and the ºBrix-Acidity ratio of the juice. Foliar urea applications increased the percentage of juice but delayed ripening. The combination of branch girdling plus foliar urea applications increased fruit weight. The yield increase was attributed to the number of fruits rather than their weight. The treatments did not reduce alternate bearing. Limitations on study/implications: The commercial cultivation areas for the experiment were limited due to the availability of facilities for testing fruit quality. Findings/conclusions: To increase the size and number of fruits, with an increase in yield, branch girdling is an effective option. Furthermore, the application of foliar urea increases the percentage of juice and fruit weight, with a slight delay in maduration. However, the treatments did not reduce alternate bearing. Future research is required with other grapefruit varieties at different application times.