Advancing, homogenizing or uniforming harvest and flowering are some of the effects that can be achieved with the use of dormancy breakers; for their application it is important to have at least 70% of cold hour accumulation, according to the requirements of each variety, and to be clear about what the final objective is.
Although every season producers evaluate the use of dormancy breakers from a productive and commercial point of view, this year the issue has been more than recurrent. And it is that Chinese New Year The “early harvest” ceremony, which will be held on January 22, has a large group of producers, mainly from early-season areas, analyzing the best strategy to reach China with their fruit before the celebration, which marks a turning point in cherry prices.
This topic was recently addressed in the article To overtake or not to overtake: the question of the moment; However, on this occasion we will analyze, with the help of Carlos Tapia, a specialist advisor in cherry production and Technical Director of Avium, a more technical area of the use of dormancy breakers.
“Deciding whether or not to use dormancy breakers and their objective must be done taking into consideration a prior evaluation of each season; the different factors that intervene in the optimal productive potential of an orchard must be combined, such as the agroclimatic, logistical-operational and commercial indicators that determine the specific objectives that each producer seeks. The decision will always go hand in hand with the vision that the producer has and what he hopes to achieve,” explained Carlos Tapia.
The proper use of dormancy breakers, considering that certain requirements must be met for their application, may allow for an advance and/or uniformity of the harvest and flowering, which, added to other factors specific to the season, could eventually translate into better profitability of the orchard.
It should be noted, for example, that for the application of dormancy breakers each variety must have reached at least 70 percent accumulation of chilling hours, according to its specific requirements. Royal Dawn, for example, needs 400 to 500 chilling hours, while Kordia needs at least 800-900 hours, based on the classic model of chilling hours accumulation, i.e. below 7.2 ºC.
It is important to consider that compliance with this requirement is essential for the use of homogenizers, but not for Hydrogenated Cyanamide, since they do not have the capacity to make up for the lack of a percentage of cold hours, a task that Cyanamide does perform to a certain extent.
But in addition to the requirements, there are certainly other questions: what type of dormancy breaker should be used, how to know if the orchard is in suitable conditions to carry out this intervention on the phenological state of the cherry tree, what risks does it entail and, of course, how to know if the results will be as expected?
“There are many questions that may arise regarding dormancy breakers and the commercial decision to use them; however, there are several aspects that must be taken into consideration. On the one hand, the decision to advance phenological states, such as flowering, setting, and harvest, mainly for early varieties, and in early areas to advance or partialize part of the surface of an orchard, in the case of a large area; on the other hand, also to advance or synchronize varieties that need to be pollinated with another variety, or “simply” based on a commercial decision depending on the current year, such as a personal vision of each producer and their strategy,” Tapia explains.
Chile and its producers have always been mostly familiar with the use of Hydrogenated Cyanamide, a product that allows advancing phenological states and harvest; however, for more than a decade, alternative dormancy breakers (RD) have been used in parallel (harmless to the plant and the operator), which are not necessarily characterized by advancing initial phenological states.
"These dormancy breakers have the ability to achieve homogenization or synchrony in the initial phenological states, even having a great power of action on the vegetative buds, generating much more flowering accompanied by leaves," clarified the Technical Director of Avium.
These dormancy breakers emerged as a response to the suspension, more than a decade ago, of the use of Hydrogenated Cyanamide in the European Community; however, in our country it continues to be used regularly and with good results. Currently, they are used separately or together, considering that Cyanamide generates a great action on the advancement of the phenological states and harvest, while RD play a more participative role in the synchrony or homogenization of said states.
Hydrogenated Cyanamide or Dormancy Breakers?
The application strategies for hydrogenated cyanamide or RD will depend exclusively on the objectives set for each orchard, taking into account, of course, the area in which it is located, the climate, correct application of the products and the calibration of the machines with which it will be carried out, among other factors.
Hydrogenated cyanamide is, without a doubt, the best tool to advance flowering; however, RDs have a characteristic that this one does not have: they homogenize and synchronize flowering, which generates great benefits from the productive point of view, since it results in nutritional, phytosanitary or growth regulator programs being more efficient.
The key is that the decision on the strategy to be used, whether with Cyanamide, RD or tandem, is based on the greatest possible amount of coherent and timely information.
“Today, with a lot of information on the subject, we can conclude that hydrogenated cyanamide alone generates a great action on the lifting of phenological states and alternative RDs, they have a great role in synchrony, rather than in advancement. But the final decision of its use must be accompanied by a clear strategy that truly benefits production and does not put it at risk. Many times it is mistakenly believed that its direct application will be effective and will allow greater profits in the season, however, there are multiple factors that influence and determine the success or failure of the production of an orchard. It is essential to make this decision with as much information as possible and establish a coherent strategy. However, doubt will always remain on our side with a decision that was made early and with an answer that we will see only in 3 or 4 months and that we hope will be accurate,” Tapia said.
It should also be noted that applications of Dormancy Breakers can generate greater risks of damage from spring frosts to the floral primordia, and in the case of darts, it can cause the death of the vegetative bud, which would be detrimental to the renewal of this reproductive organ.
The phenological stage requiring the greatest care is the swollen bud, where the plants are most sensitive to cold damage. This makes it necessary that, in the event of low temperature episodes (<-0.5ºC for more than one hour), frost protection systems are required. According to data provided by Avium, there are records of significant damage between the swollen bud and exposed bouquet stages, over more advanced stages, such as white bud or full flower.
Another aspect to consider is that although the use of these strategies allows for earlier flowering, this does not mean an earlier harvest of the same number of days. For example, an advance of 10 days in full flower does not translate into 10 fewer days of harvest, but rather 5-6 days; meanwhile, in a season with a very good accumulation of cold, an advance of 20 days in full flower could become about 10-12 fewer days of harvest.
This was confirmed in a study carried out by the Avium team, in relation to the impact of dormancy breakers on the advance of the harvest and concentration of flowering; for this purpose, 50% hydrogenated cyanamide (CH) and alternative dormancy breakers (RD) (Fiore® and Erger®) were used in the 2015/2016 season of the Santina variety. The objective of the trial was to evaluate the different strategies to verify whether it is possible to achieve a homogenization of the initial phenological states of the cherry and, eventually, achieve a significant advance in the harvest, which would result in greater profitability in production.
Finally, it should be noted that the decision to use RD must be accompanied by a clear strategy that contributes to production and in which ideally there are no risks that could affect the initial objective. How and when to use them, whether hydrogenated cyanamide or a dormancy breaker, becomes a fundamental decision that depends on several requirements that will define the success or failure of this commercial strategy and, as a consequence, determine the productive potential of the orchard.
