By: Ricardo Rojas, Agricultural Engineer – Avium Technical Advisor; Bruno Tapia, Agricultural Engineer – Avium Technical Coordinator; Diego Húmeres, Avium Climate and Irrigation Department; Carlos Tapia, Agricultural Engineer, M.Sc. – Avium Technical Director.
To achieve the maximum productive potential in an orchard, it is essential to plan the pruning strategy based on maintaining and renewing the different productive structures of the tree. The success of this work is directly related to the time of year in which it is carried out and under what conditions and objectives it is executed.
Every day, the question arises: kilos or quality? There is no correct answer, but it is a question that is resolved as the productive potential of each unit is known, and at the end of the road everyone agrees on the concept “KILOS AND QUALITY”, this is called productive potential. This potential is related to the energy material in the fruit’s dry matter and its structures. In the case of cherries, among the quality parameters most recognized by consumers are the size, firmness and condition of the fruit, therefore, the objective must be to achieve the maximum yield in kilos that maintains the maximum quality of the fruit.
To achieve the maximum productive potential in an orchard, it is extremely important to build a history in each productive unit. To do this, there are different types of analysis that generate information of great importance for decision-making at the orchard level.
Among the minimum analyses that must be considered for a good pruning and load regulation strategy are:
- Bud fertility analysis: It corresponds in numerical or quantitative terms to the number of flower buds that the fruit centers have, mainly darts, and the number of healthy and damaged flower primordia that each of the flower buds have, to reveal the number of flowers or flowering potential that these structures have.
- Counting fruit centers: Quantification of the shoots, mainly, allows us to know the productive potential. Ideally, our counting units should be defined, under the criteria of uniformity and health of the plant. In addition, it is advisable to mark each of the plants, in order to create monitoring stations which should be followed throughout the season.
- Reserves analysis: To date, there is no consensus on establishing a protocol and parameters of appropriate ranges for reserve analyses in fruit centers to generate information for decision-making.
The Avium team has been following the analysis of nitrogen reserves (Arginine, total N and total protein) and carbon reserves (Starch) for several seasons, considering that their results also depend on the position of the fruit centre in the tree, and the age of the branch section from which they are collected. It is important to be able to build comparative parameters over the years in each productive situation.
Each of these analyses is of great relevance in the construction of the productive potential expressed in kilos. In many fruit species, including cherry, knowing the magnitude of this value expressed in kilos per hectare and at the same time knowing the distribution of sizes is of enormous interest to the commercial area, but from the technical point of view its correct estimation is very complex.
There are producers who have managed to consistently build this number, and it coincides with the fact that they have a good management of field information and that they have been able to perfectly identify the distribution of
quality of the plants, even carrying out different management for each of them. At this point, the use of new technological tools that help measure parameters within the orchard that help to discriminate types of plants and more complex areas becomes relevant.
Throughout the seasons, Avium has identified the need to be able to formalize and remember management concepts, especially in pruning and load regulation tasks. The guidelines and instructions generated in different situations often lack technical precision when giving guidelines or in simple field analyses. Below is a brief summary, with personal definitions, with examples of the most recurrent procedures in the management of the different structures.
- Renewal pruning.
The main objective of the concept of renewal pruning is to renew (or remake) the “primary” or “permanent” structure of the plant. In general, this is material that generates excessive shade during the season and is no longer a protagonist in production due to the lack of fruit centers.
Many times these structures are young, “suckers” with excess vigor, with a diameter similar to the axis of the plant, which will not be used for a future productive branch unless they are intervened (Photos 1 and 2).
The idea is always to be able to “eliminate” this type of material, leaving a “base block” to accommodate future renovations and not lose that point in the primary structure of the plant (Photos 3 and 4). It is important to be clear that the concept itself is not “eliminate” but rather, the concept
It involves multiplying the growth point, allowing for more balanced branches that enter the productive stage more quickly (Photo 5).
Since you are making cuts in “thick” material, the idea is to always cover them with some type of post-pruning paste or paint.
- Branch pruning.
The concept of pruning is defined as the intervention of wood for one year in winter, or less than one year in the case that it is carried out in green in spring/summer (Photo 6 and 7).
The purpose of pruning is to promote vegetative development just behind the section in which the cut is made, seeking to give the wood involved a “second wind”. In this way, vegetative development is promoted and premature formation of darts (premature browning) is avoided.
This work must be distinguished between situations of dwarfing rootstocks and in cases of vigorous rootstocks. In the first case, this work is necessary to ensure “vigor” since it promotes vegetative development, but in the case of vigorous rootstocks, this work could be a mistake since the cut acts as a sign of juvenileness, which negatively harms the formation of fruit wood. It is still heard that this intervention of one-year-old twigs promotes “darkening” but this concept is wrong since it is exactly the opposite.
- Pruning or thinning branches.
The concept of pruning or thinning branches involves intervening in branches that have fruit structures (darts) in sections that are two years old or older. The main objective of this is to adjust the load early in order to be able to do without fruit centers when they are in excess, a situation that is very characteristic of weak combinations.
This intervention is carried out just after a new year's ring or in a section that generates self-support of branches (Photos 9 and 10). The intensity with which this work is carried out depends directly on the length of the branch.
In certain fruit species, early pruning is a very common practice in tree formation and later pruning induces the formation of shoots only when there is an imbalance between vegetative and reproductive growth, generating an increase in fruiting (Gil, 2012). In the case of cherry trees, this is not entirely resolved.
The concept of self-supporting branches considers that the fruit contained in that section of branches is supported by its structure, ensuring vegetative development and generating a more regular result in terms of balance in fruit size and composition of sugars and nutrients (Photos 11 and 12).
- Bud thinning or extinction.
Within the concept of “thinning” of structures, the thinning or extinction of buds, also called “Chinese thinning” (Photos 13, 13 and 14) is by far the most effective when compared to the thinning of flowers and fruits that have already set.
The removal of flower buds is a strategy that not only aims to reduce the fruit load, but is also the best strategy to ensure the vegetative balance of the plant and even the safest model to recover stressed plants and in a vicious circle of permanent weakness.
The intensity of bud thinning in terms of bud removal will depend on the results of the bud fertility analysis as the objective tool that allows an accurate decision to be made. This is also associated with the fertility of the variety, rootstock, training system and also the vigor or weakness of the combination.
- Thinning or extinction of darts.
In other fruit species, the elimination or extinction of fruit centers is a common and successful practice. However, in cherry trees, the extinction of shoots becomes a huge mistake when defining the thinning or load regulation strategy.
The dart itself is the fruit structure that is renewable year after year, since it contains at least and commonly one vegetative bud that is responsible for generating leaves, and in its axils it houses new flower buds every season (Photos 15, 16 and 17).
For this reason, the removal of a shoot is the irreversible loss of a fruiting point. The only extinction of shoots that is justified could be that in a section of the change of year ring in exchange for carrying out a cut or reduction in this area.
It is important to remember that any type of pruning or thinning strategy chosen must be accompanied by an orchard that is in optimal phytosanitary conditions, that is, a healthy orchard, with all its programs up to date and of course the decision must be in line with the productive objectives sought.
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