Summer Pruning Techniques for Modern Apple Dwarf High-Density Orchards
In recent years, a large number of dwarf high-density apple orchards have taken root in various regions. However, the old revolution has encountered new problems, and many bases have not truly understood and mastered the new cultivation model. Dwarf high-density cultivation places emphasis on summer pruning. What kind of management approach should we adopt to match it?
Modern dwarf high-density orchards often use large branched trees on own-rooted rootstocks to establish the orchard, cultivating a "wall-type" structure through wide-row high-density planting, equipped with corresponding mechanical equipment, to achieve the goals of labor-saving, standardization, and large-scale production. Because an entirely new cultivation model is adopted, traditional management methods no longer apply, and everything from tree form to pruning changes accordingly.
Traditional orchards use small single-trunk trees to establish the orchard, and the target tree form ultimately cultivated is often a large-canopy tree form, so the juvenile stage focuses on promoting growth, and winter pruning is widely used in production, with the practice of heading back to expand the canopy. Fruiting also follows the idea of growing the tree first and then bearing fruit, generally leaving no fruit for the first 3 to 4 years. For modern dwarf high-density orchards, however, because large branched trees are used to establish the orchard and the target tree form is a small-canopy tree form (tall spindle, canopy width within 1 m), the management approach in the juvenile stage generally focuses on suppressing growth, with extensive use of summer pruning. For fruiting, the approach is to grow the tree and bear fruit at the same time, using an appropriate amount of fruit in the early stage to control the canopy.
Traditional fruit trees generally have about 5 permanent large scaffold branches (modified leader form), each scaffold branch equipped with side branches and fruiting branch groups, with great attention paid to the basal angle, waist angle, and tip angle, and to the size, position, and orientation of side branches. Cultivating a single scaffold branch takes many years, so the cultivation of each scaffold branch is meticulous and strict. After the scaffold branches are successfully cultivated, pruning management consists of local minor adjustments, and the framework no longer changes; summer pruning often only deals with some vigorous watersprouts on the back. For the tall spindle tree form in dwarf high-density orchards, however, the whole tree has 40 to 50 temporary scaffold branches, and the retention or removal and management of a single scaffold branch has little effect on the whole tree. At this point, tree form management no longer focuses on the individual, but takes the whole tree or the population as the starting point.
When pruning traditional fruit trees, we value the response of the bud at the cut, because we are cultivating branches; there used to be a saying, "Whether you pruned well or not, you can tell by the tree's response." With modern tall spindle tree form pruning, we look at the response of other branches; the pruned branch is often renewed after 1 to 2 years. This kind of pruning is making choices: the whole tree has many branches, and we keep the good and suitable ones and cut back or remove the ones that are too large or poor. So how can we ensure that there are many branches on the tree every year for us to choose from? Actually it is very simple: when removing large branches, we leave a "live stub," that is, instead of the traditional removal flush with the base, we leave a short stub to ensure 2 to 3 latent buds sprout the following year.
Therefore, the basic approach to pruning modern dwarf high-density orchards is: first, summer pruning as the main method; second, bearing fruit while growing the tree, using fruit to suppress the canopy; third, focusing on the population, so a uniform cut can be made; fourth, changing from branch cultivation to branch selection.
In view of the above approach, and combined with our company's 3-year-old dwarf high-density orchard, I will briefly discuss some summer pruning methods.
The variety demonstration orchard of Baoji Huasheng Fruit Industry Co., Ltd. is located in Yingming Village, Shuigou Town, Qianyang County, with an area of 100 mu. The main variety is Michenla (a Gala variety bred in New Zealand), and there are also displays of varieties such as rust-free Golden Delicious, Fujiku, Fubulasi, Modi, Buckeye, Honeycrisp, Shengnühong, Aidahong, Aisda, and Granny Smith. The first planting was in May 2014, using imported large branched trees, M 9-T337 own-rooted rootstock, with a spacing of 3.5 m x 1 m, integrated fertilizer and water management, and grass growing between rows. So far, tree height has reached more than 3.5 m, with more than 40 branches, and after winter pruning in 2015 the number of branches per mu reached 40,000. This year, the fruit retained per tree is 100 to 120, and the expected yield per mu is 2,000 to 3,000 kg.
At present, the tree vigor is slightly vigorous, some branches are too long, and the lower part of some trees is relatively dense between plants. The goal of summer pruning is to further standardize the tree structure, maintain single-axis extension of scaffold branches, straighten out the branches, moderately control vigorous growth, and adjust the fruit load and light in individual cases so that sunlight can enter the inner canopy. The specific measures are as follows:
1. Cut back overly long large branches between rows. On the basis of winter removal, at this time cut back some overly long large branches that are bearing fruit temporarily. When cutting back, be careful to leave a flat-angled, relatively weak branch as the leader. Generally, cut off the part of the branch extending into the inter-row space, accounting for about 1/5 to 1/4 of the length of that branch. At the same time, if there is enough fruit at the base of the branch and near the inner canopy (generally 5 to 8 fruits), the overly long tip portion and excess fruit can be removed together. If there is insufficient fruit at the base and in the inner canopy, it needs to be handled comprehensively according to the fruit retention situation of the whole tree.
2. Remove overly large upright branches in the upper part. In tall spindle tree form training, generally speaking, timely branch bending in the first two years can cultivate a large number of excellent scaffold branches. Entering the third year, considering labor savings and other factors comprehensively, branch bending is generally no longer carried out. For relatively large upright branches in the upper part of the tree, if they have not formed a large amount of flower buds and fruit, consider removing them directly at this time.
3. Remove competitive branches at the extension shoot of the scaffold branch and overly long branches in the middle of the scaffold branch. After tall spindle scaffold branches are left unpruned, their extension shoot easily forms double forks, triple forks, and multiple forks. If allowed to grow, this will disrupt the tree form and affect light, so it should be removed at this stage. In addition, to ensure single-axis extension of the scaffold branch, large side branches on the scaffold branch also need to be removed.