Productive characteristics of ‘Golden Reinders’ apple nine-month nursery trees improved by 6-BA and nitrogen fertigation

Abstract

In this study, 6-benzyladenine (6-BA) and nitrogen fertigation were used to improve branching of nine-month old apple ‘Golden Reinders’ nursery trees grafted on ‘M9’ rootstock. The upper third of nursery trees was treated weekly with 6-BA, 3 times in June in concentration of 0, 300, 600, 1,200 and 1,800 mg L-1. Nitrogen (N) was also added weekly, at total amount of 50, 100, 150 and 200 kg ha-1 for a season. Parameters of nursery tree quality (trunk cross-sectional area (TCSA), height of nursery tree and the number and quality of lateral branches) were evaluated at the end of the growing season. Their classification was done according to number of lateral branches longer than 30 cm in the two groups, as follows: 1) nursery trees with 5 or more lateral branches (5+) and 2) nursery trees with 3 or 4 lateral branches (3+). These nursery trees were then planted in high density orchard (3,470 tree ha-1) and their productive characteristics were tested with three levels of crop load during the second (2015) and the third growing year (2016). Low crop load (LCL) included 10 fruit in the second and 40 fruit tree-1 in the third year, moderate crop load (MCL) included 20 fruit in the second and 65 fruit tree-1 in the third year and high crop load (HCL) included 30 fruit in the second and 90 fruit tree-1 in the third year. Application of 6-BA and N enhanced diameter and height of trees in the nursery. The height of the tree was however more influenced by the application of N. Total number of lateral branches and number of branches longer than 30 cm were increased in the treatments with 6-BA, whereby any increase in its concentration significantly increased the number of lateral branches. The same trend was also observed with application of higher N concentration. Additionally, the interaction of these two factors significantly enhanced their individual effect. In the orchard, during the second year, the yield increased significantly with the increase of the crop load, but fruit size did not differ significantly. HCL provided the highest total yield and the yield of fruit with diameter >70 mm in both examined groups of nursery trees. There were no differences among the number of fruiting buds tree-1 loaded with different numbers of fruits. The trees belonging to class 5+ had a significantly higher yield and number of fruit buds for the subsequent year compared to the trees belonging to class 3+. In the third year, a higher crop load increased the total yield tree-1, but reduces the average weight of the fruit. HCL trees had the highest yield and reduced fruit weight compared to the other treatments, but all fruits showed a diameter >70 mm. However, number of fruiting buds tree-1 was significantly reduced compared to the other two treatments and was not enough for regular yields in subsequent year. MCL trees had high yield and enough number of fruiting buds for full productivity in the fourth year. © 2022 International Society for Horticultural Science. All rights reserved.