Bud analysis is widely known for the information it provides based on the number of buds per dart, number of damaged and healthy floral primordia per bud per dart, the latter being the most important, since the 90% of the damaged primordia occurs at the beginning of dormancy, where this damage is mainly associated with poor lignification of the floral centers and/or poor formation of bracts; Why does this damage occur? Mainly due to cold, therefore frost events at the end of April or beginning of May are the main causes of this damage, this is because the plants during this date are advancing in their lignification process and coverage of bracts in their floral structures.
That said, as the seasons go by, bud analysis has become more important as an important tool in making early technical decisions, seeking to reduce uncertainty with the flowering potential of each orchard, being one of the factors that come into play to define a correct productive equation. It is also a tool where the history of the orchard for each season can be built, producing an important database that can be analyzed and thus project measures that go in line with understanding the floral offer for each situation.
Productive potential:
In the event of low flowering potential, i.e. less than 15 flowers per fruit center (FC), it must be addressed conservatively, where the first stage in load regulation is pruning, where precautions must also be taken to ensure the viability of the flowers or their subsequent setting, achieving fruit retention through the use of some growth regulator.
In the case of having high and excessive ranges, it is necessary to worry about a good accumulation of cold hours, a spring with favorable temperatures and conditions for pollination and fertilization, which could translate into an eventual high fruit set, so it could be necessary to define a joint pruning strategy, early bud thinning and/or fruit thinning if the need is seen in the latter, ending 30 days after full flower.
Undoubtedly, when calculating the productive potential of an orchard, in addition to the considerations described regarding the number of healthy flowers per fruit center, it is also associated with the percentage of fruit set of each variety, and that in itself when evaluating this factor, different figures can be obtained, in addition to adding the variety/rootstock combination, climatic zones, phytosanitary conditions and homogeneity of the orchard, among various factors that must be taken into consideration for assertive management when carrying out management based on these numbers.
This load analysis becomes more important considering that according to the productive evidence of the last years of production in Chile, considering the kilos per ha produced in orchards of 4 years and more at the national level as an average (internal data not published), it indicates that there is a production pattern that has been marked, where a year of high production can be seen and the subsequent 2 years of lower productivity, always being the year following the year of high production the lowest with respect to the following year. Understanding this pattern, and eventually with fertility rates that could be higher this 2023-24 season compared to the last two, this year the pruning work could be very important with the objective of load regulation, being the one that can generate an important impact in terms of the quality and condition of the product, as well as the cost control with respect to the tasks that could be involved later to obtain a maximum in the production of the crop.
Pruning
Although it could be a matter of training, renewal and maintenance of the conduction system, we will focus on production, taking it as the most effective and economical tool to early adjust the potential fruit load. This is the most effective method for regulating load, since the intensity of the load can be decided based on the number of fruit centers per hectare or fruit centers per plant.
According to the above, and to the extent that the cherry bud fertility analyses (AdYC) this season indicate that it may be a year of high load, this task is positioned as the most attractive for the industry and that according to the reproductive material that is in each orchard (shoots and twigs), the intensity of pruning can lead to a stronger pruning strategy.
Given this scenario, precautions must be taken to obtain an adequate vigor/productivity ratio, in the sense that there could be greater vegetative expression with this type of "strong" pruning; excessive shoot growth could be observed, which would alter the condition of the fruit in terms of its condition and quality given the sink effect of this structure.
Bud thinning
Also known as “Chinese thinning”, it is the removal of flower buds from the shoot, with the aim of reducing the fruit load early in the season, where its main objective is to improve the size of the fruit, although it 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.
This strategy, although expensive, if pruning is considered as the first filter for load regulation, is still a task that should undoubtedly be carried out when the productive potential is very high compared to the condition of each orchard, where important benefits are obtained in terms of the condition and quality of the fruit, with the size being the most important attribute for the industry in this last point.
Extinction of darts
While in other species the elimination or extinction of fruiting centers is a common and successful practice for load regulation, in cherry trees the extinction of shoots becomes a huge mistake when defining thinning or load regulation strategies if it is not accompanied by a field analysis defining the real need. This is because the shoot itself is the renewable fruit structure year after year, since it contains at least and commonly one vegetative bud which is responsible for generating leaves, and in its axils housing new floral buds every next season, and it is for this reason that the elimination of a shoot is the irreversible loss of a fruiting point. Based on the analysis of the behaviour of the shoot in the cherry tree, it is only justified to carry out this task of eliminating shoots when it is desired to eliminate a section of the new year's ring in exchange for carrying out a cut or reduction in this area or also and in very special situations where there are 2 or more shoots in a single fruit centre, generally found in orchards with a high flowering potential, weak rootstocks and high setting varieties.
Research carried out in Chile in the past (Table 1) has shown that these load regulation strategies are successful.
Table 1 below shows the yields and fruit size, illustrating that all types of thinning were effective in these fairly fruitful orchards. It can be seen that bud thinning was the most effective, but that the more delayed fruit thinning was also effective in restoring the size of these overloaded trees.
Table 1. Production results (kg/ha and kg/ASTT) and average fruit weight (g) for each thinning treatment in the Lapins and Sweetheart cultivars. Kulzcewski and Tapia 2021.
It should be taken into consideration that this tool must be used judiciously depending on the rootstock/variety combination mainly, since an excessive flowering potential according to the infographic for self-incompatible varieties such as Regina and Kordia does not have the same interpretation in practice to regulate the load with strong pruning or thinning, however when compared to a self-fertile variety such as Lapins, strong pruning and bud thinning must be performed.
An early load adjustment, either with pruning and/or thinning, depending on the specific need, will be the best tools to achieve the objective of reaching a fruit caliber curve, where the sum from 28 mm upwards is at least 70%. It is known that the greater the distance between the load adjustment at full flower, the greater its impact on caliber and soluble solids, which can be observed at harvest, with caliber being the most commercially important, as has been observed in recent export seasons and returns to producers.
The use of load regulation techniques is mainly determined by the background information provided by the AdYC for each variety/rootstock combination, vegetative state, health condition, among other factors, where not carrying out this action is much more costly when the orchard warrants it.
