Document Type : Research Paper - Pomology
Authors
1 M.Sc. Graduate of Horticultural Science, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran
2 Assistant Professor, Department of Horticultural Science, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran
3 Associate Professor، Department of Horticulture Science، Faculty of Agriculture، Shahid Chamran University of Ahvaz، Ahvaz، Iran
Abstract
Introduction
Olive trees are among the most important fruit crops globally, with particular importance in both the Iranian and international fruit production industries. During the past decades, in Khuzestan province, like in several other regions, many olive orchards were established without considering the selection of suitable cultivars. As a result, these trees face various issues related to flower production, such as insufficient flowering, poor fruit set, and a decrease in oil content. Several methods can address these challenges, with girdling be one of the most effective. Girdling, a method of bark pruning, encourages early flowering and fruiting, thereby enhancing the tree's productivity. This research aimed to investigate the effects of girdling at different times on the flowering and biochemical characteristics of three olive cultivars (Conservalia, Roghani, and Mission), which are known for poor flower production.
Materials and Methods
This experiment was conducted at the olive research orchard of the Faculty of Agriculture at Shahid Chamran University of Ahvaz, using 20-year-old olive trees during the 2022-2023 growing season. The study investigated the effects of girdling on the quantitative and qualitative aspects of flower production as well as certain biochemical indicators. The experiment followed a split-plot design within a randomized complete block design, with four replications. The main plots included three olive cultivars (Conservalia, Roghani, and Mission), and the sub-plots consisted of four girdling treatments: control (no girdling), and girdling conducted in January, February and March.
Results and Discussion
The results revealed that girdling at all times increased the number of flowers per inflorescence compared to the control treatment. The highest number of flower in the inflorescence was observed with January girdling (18.17), which was more than double the control (9.1). The Roghani cultivar produced the highest average flower count per inflorescence (14.87). January girdling also resulted in the highest percentage of complete flowers (49.92%), with the Mission cultivar showing the highest percentage of complete flowers (45.31%). The relative water content in leaves was highest with January girdling (84.49%), significantly surpassing the control, February and March treatments. The Mission cultivar had the highest relative water content at 72.33%. Girdling significantly increased the fresh leaf weight in ringed branches, with the effect was diminishing from January to March. Roghani exhibited the highest leaf dry weight (14.94 g), which was not significantly different from Mission's leaf dry weight (13.69 g), but was significantly higher than Conservalia's dry weight. The highest leaf dry weight was recorded with January girdling (17 g), which was significantly higher than the other treatments. In terms of total soluble carbohydrates, the highest amount was observed in the Roghani cultivar in June (22.23 mg/g). Girdling increased total soluble carbohydrate content, although this effect diminished from January to March. Overall, girdling improved flowering traits, with increased numbers of flowers, fresh and dry flower weight, and a better flowering initiation. Roghani and Mission cultivars exhibited superior results in terms of flowering characteristics, carbohydrates, leaf water content, and leaf dry weight.
Conclusion
The immediate effect of girdling is the restriction of sap flow from the leaves to the roots, leading to the accumulation of sugars and plant hormones in the upper part of the tree. These accumulated materials are then transferred to the growing buds and inflorescences, promoting their development. . In this experiment, girdling was shown to improve flowering characteristics, with January being the most effective time for girdling across the olive cultivars tested. Therefore, January girdling is recommended for improving flowering and productivity in olive trees in the Ahvaz region.
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