Pruning and Load Regulation for Orchard Development

Pruning and Load Regulation for Orchard Development

By Carlos Tapia, Agricultural Engineer, M.Sc., and Technical Director at Avium and team*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 task is directly related to the timing, conditions, and objectives of its execution.

Every day, the question arises: “Quantity or Quality?” There is no right answer, but rather it is a question that is solved as the productive potential of each unit is understood, and in the end, everyone agrees on the concept of “Quantity AND Quality,” which is referred to as productive potential. This potential is related to the energy material in the fruit’s dry matter and its structures. For cherries, size, firmness, and fruit condition are among the quality parameters most recognized by consumers. Therefore, the objective should be to achieve the maximum yield in kilos while maintaining the highest fruit quality.

To achieve the maximum productive potential in an orchard, it is of utmost importance to build a history for each productive unit. To do this, various types of analyses generate essential information for decision-making at the orchard level.

Among the minimal analyses to be considered for a good pruning and load regulation strategy are:

Buds fertility analysis: This involves quantifying the number of floral buds in the fruiting spurs, mainly buds and the number of healthy and damaged flower primordia in each of the floral buds, revealing the amount of flowers or potential for flowering that these structures have.

Fruiting spurs counting: Quantification, mainly of buds, to determine the productive potential. Ideally, our counting units should be defined based on the criteria of uniformity and plant health. Also, it is advisable to mark each plant to create monitoring stations that should be followed throughout the season.

Reserves analysis: So far, there is no consensus on establishing a protocol and suitable range parameters for reserves analysis in fruiting spurs to generate reliable information for decision-making.

The Avium team has been following nitrogen reserves analysis (Arginine, total nitrogen, and total protein) and carbon reserves analysis (Starch) for several seasons, considering that their results also depend on the position of the fruiting spur on the tree and the age of the branch section from which they are collected. It is essential to build comparative parameters in the years for each productive situation.

Each of these analyses is of great relevance in building the productive potential expressed in kilos. In many fruit species, including cherries, knowing the magnitude of this value expressed in kilos per hectare and understanding the distribution of calibers is of significant interest to the commercial area. However, from a technical point of view, its correct estimation becomes very complex.

There are producers who have consistently constructed this number, and it coincides with having good management of field information and being able to identify plant quality distribution, even implementing differentiated management for each of them. At this point, the use of new technological tools becomes relevant, helping to measure parameters within the orchard that discriminate between different types of plants and more complex areas.

Throughout the seasons, Avium has identified the need to formalize and remember management concepts, especially in pruning and load regulation tasks. Guidelines and instructions generated in different situations often lack technical precision when providing guidelines or during simple field analyses. Below is a brief summary, with personal definitions and examples of the most recurring procedures in managing different structures.

Renewal pruning:

The concept of renewal pruning aims primarily to renew (or rebuild) the “primary” or “permanent” structure of the plant. Usually, this includes material that generates excessive shade during the season and is no longer productive due to the lack of fruiting spurs.

Many times, these structures are young, “suckers” with excessive vigor, with a diameter similar to the plant’s axis, which will not be used for future productive branches unless intervened (Photos 1 and 2).

The idea is always to “eliminate” this type of material, leaving a base “stub” to accommodate future renewals and not lose that point in the plant’s primary structure (Photos 3 and 4). It is important to be clear that the concept itself is not about “elimination” but rather about multiplying the growth point, allowing for more balanced branches that enter the productive stage more quickly (Photo 5).

Since cuts are made in “thick” material, it is essential to always cover them with some type of post-pruning paste or paint.

Branch tipping:

The concept of tipping is defined as the intervention of one-year-old wood in winter, or less than one year old if done in green during spring/summer (Photos 6 and 7).

The tipping aims to promote vegetative development just behind the section where the cut is made, ensuring that the intervened wood has a “second chance.” In this way, vegetative development is promoted, and the early spur development is avoided.

This labor needs to be differentiated between situations of dwarfing rootstocks and cases of vigorous rootstocks. In the first case, this work is necessary to ensure “vigor” as it promotes vegetative development. Still, in the case of vigorous rootstocks, this labor could be a mistake as the cut acts as a signal of juvenility, negatively affecting the formation of fruiting wood. It is still heard that this intervention of one-year-old sprouts promotes the early spur development, but that concept is incorrect as it is exactly the opposite.

Branch recutting or reducing:

The concept of recutting or reducing branches involves intervening branches that bear fruiting structures (buds) in sections of two years or more. This aims to adjust the early load to dispense with fruiting spurs when they are excessive, a characteristic situation in weak combinations.

This intervention is performed just behind a ring of age change or in a section that generates self-support of branches (Photos 8 and 9). The intensity with which this work is carried out depends directly on the length of the branch.

In certain fruit species, early tipping is a very common practice in tree formation, and later tipping induces the formation of buds only when there is an imbalance between vegetative and reproductive growth, resulting in increased fruiting (Gil, 2012). In the case of cherries, it is not entirely resolved.

Self-support of branches concept considers that the fruit contained in that section of branches is supported by its structure, ensuring vegetative development and generating more consistent results in terms of fruit size and sugar and nutrient composition (Photo 10).

Bud thinning or extinction:

Within the concept of “thinning” of structures, bud thinning or extinction, also called “Chinese thinning” (Photos 11, 12, and 13), is by far the most effective when compared to thinning of bloomed or set fruits.

Removing flower buds is a strategy that not only aims to reduce fruit load but is also the best strategy to ensure the vegetative balance of the plant and even the safest way to recover stressed plants caught in a vicious circle of permanent weakness.

The intensity of bud thinning in terms of elimination depends on the result of the fertility analysis of buds, as an objective tool that allows for accurate decision-making. This is also associated with the fertility of the variety, rootstock, training system, and the vigor or weakness of the combination.

Thinning or extinction of fruiting spurs:

In other fruit species, the elimination or extinction of fruiting spurs is a common and successful practice. However, in cherries, the extinction of fruiting spurs becomes a huge mistake when defining thinning or load regulation strategies.

The fruiting spur itself is the renewable fruiting structure year after year, as it contains at least one and commonly one vegetative bud responsible for generating leaves and housing new flower buds every season (Photos 14, 15, and 16).

For this reason, the elimination of a fruiting spur is the irreversible loss of a fruiting point. The only extinction of fruiting spurs that may be justified is that in a section of an age change ring when making a recutting or reducing in this area.

It is important to remember that any type of pruning or thinning strategy chosen must be accompanied by a well-maintained and healthy orchard, with all programs up to date, and, of course, the decision must be in line with the productive objectives being pursued.

*Contributed to this article: Ricardo Rojas, Agricultural Engineer and Technical Advisor at Avium; Bruno Tapia, Agricultural Engineer and Technical Coordinator at Avium; Diego Húmeres, Climate and Irrigation Department at Avium.

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