Effect of pruning systems on phenological, morphological and fruit characteristics of hazelnut

This research was carried out to determine the effect of different pruning systems on phenological, morphological and pomological characteristics of 'Çakıldak', 'Foşa' and 'Tombul' hazelnut (Corylus avellana L.) cultivars. Hazelnut plants were subjected to 5 different pruning systems: ocak, free vase, single vertical system, double vertical system and multiple vertical system. The trees were planted at a planting density of 5.0 x 4.0 m in the ocak system; 5.0 x 4.0 m in the free vase system; 5.0 x 1.35 m in the single vertical system; 5.0 x 1.35 m in the double vertical system and 5.0 x 2.0 m in the multiple vertical system. In the study, phenological observation and morphological measurements and nut characteristics were invesigated in 2021, 2022 and 2023. In the final two years of the study, the trunk cross-sectional area and trunk diameter of 'Tombul' hazelnuts pruned in the double vertical system were higher than those pruned in the ocak system. However, in 2022, the trunk cross-sectional area and trunk diameter of the 'Foşa' cultivar in the ocak system were significantly greater than those of the other pruning systems. In 2021, the number of shoots of the 'Çakıldak' and 'Tombul' hazelnut cultivars pruned in the ocak system was significantly higher than those in other pruning systems. In contrast, shoot diameter was lower. In the final two growth periods of the experiment, it was observed that the tree volume of 'Çakıldak' hazelnut trees pruned in the single vertical system was greater than that of trees pruned in the ocak system. In the year 2023, the nut weight, width, length and thickness of shelled and inner 'Tombul' hazelnuts pruned in the single vertical system were greater than those of the trees pruned in the ocak system. Furthermore, the leaf area of 'Tombul' hazelnut trees pruned in free vase and single vertical system was found to be lower than the leaf area of trees pruned in other systems. As a result, it has been revealed that pruning systems have significant effects on both morphological and nut characteristics of hazelnut plants.