In a season like this, where we face different situations every week that complicate the production of cherry trees, we can point out in a transversal way that the deficiency of cold accumulation in the dormancy stage of the plants is one of the factors that marks the guideline if we talk about limiting the production potential of orchards, this added to the low temperatures in the stage of exit from dormancy and rains associated with the flowering and fruiting period.
Let’s take Chile as an example, in these last 20 years of cherry production, the low production associated mainly with cold deficiency in the seasons is notable.
If the accumulation of cold (measured in hours of cold based on 7.2ºC) is compared, the hours of this season versus the averages in the last 10 seasons, it is approximately 30% below.
This deficiency began to be observed with very uneven and irregular flowering, fruit centers that did not open, poor fruit set and very late sprouting, to which we added the rains during flowering and in some cases, waterlogged soils, finally allowing the outcome to be even more complicated.
Regarding non-uniformity, it was more highlighted in those varieties that require greater accumulation of cold and earlier flowering such as Royal Dawn, Santina and Bing; Although Lapins is one of the varieties with the lowest cold requirements, this non-uniformity could also be evidenced, but to a lesser extent. With all of the above, it is very likely that the decrease in volume for this year in relation to the estimates will be around 25-30% less than last season.
Management that minimizes the effects of cold deficiency
The most used treatments to deal with cold deficiency are related to: 1) improving the state or quality of plant dormancy, 2) intervening to a lesser extent on the plant (pruning) in order to increase the number of fruit centers. Another management recently used is related to evaporative cooling, the result of which is associated with a decrease in the temperature of the buds.
Regarding the first point, an important management is to induce recess of the plants, through regulated stimulation that favors the entry into recess. We know that this stage is also associated with low luminosity and changes in temperature that begin to occur in the environment, therefore, it is not good to make late fertilization contributions, particularly nitrogenous, or excessive irrigation that promote greater activity.
Then, apply dormancy breakers such as hydrogenated cyanamide in higher doses than those normally applied, in order to promote more uniform states of flowering and budding. However, in any case the productive results will be associated with different climatic indicators in the flowering period.
Utility and efficiency of the use of shade in recent years
Another way in which the quality of cold is evident in relation to the productive potential of trees is often associated with natural factors that imply shading given by: hills, living fences, structures, etc. In simple observations, it has been possible to measure and quantify the productive increase associated with this quality of shade.
It should be considered that the dormancy stage is not only defined by the amount of cold accumulated in the cycle, but also regulated by the length of the photoperiod, which being shorter, assumes a better quality of dormancy.
On the other hand, the models for measuring and recording of cold accumulation, in their different versions, consider environmental temperature scales for these calculations, but none of them consider the temperature of the bodies (trees or fruiting structures), which can benefit with the use of shadow.
On this point we can verify scientific evidence that has demonstrated the use of shade to improve the quality of cold and thus increase productivity. This behavior is associated with: uniformity and earlier flowering, and greater fruit set per center. The above, also associated with other complementary technical management.
This behavior is undoubtedly reflected in those years of poor cold accumulation, since in good cold years the differences are not so significant.
Use of shade nets
The cultivation of cherry trees in several countries occurs mainly in areas that meet the appropriate environmental conditions during winter and spring to guarantee the quality and synchronization of flowering and its subsequent processes, supported by optimal climatic indicators.
The use of covers of all types in agriculture has become an important tool to mitigate adverse environmental conditions. Some examples are rain tents, shade nets and anti-hail nets. In particular, the use of shade nets has become increasingly common in the production of fruit trees such as apple trees, blueberries and now also in cherry trees.
These covers have different uses depending on the type of crop; In the case of the first type, they are used to obtain a greater color in the fruits, delaying their ripening, obtaining later harvests (Rodríguez and Morales 2015) this due to the modification of the microclimate under these covers that directly affects the physiology of the plants and the development of the fruits (Valdebenito 2020), also to prevent sun damage to the fruits.
In the case of cherry trees, they are used to allow the trees to go into recess appropriately, through forced modification of the photoperiod, and in winter, shortening the photoperiod, generating a higher quality dormancy stage. These covers are definitely an effective solution to protect crops and guarantee their optimal development in unfavorable climatic conditions depending on the various objectives for each case.
The use of shade netting in cherry orchards aimed at early harvests seeks to reduce solar radiation to create a short day environment, and enter and improve quality in the recess stage. This technique studied, among others, by Ruiz et al (2005), where they shaded complete damascus trees and parts of them (Image 1), demonstrated a significant decrease in the intensity of solar radiation in the shaded branches, which in turn reduced the temperature in the tree structures.
They also observed a higher incidence of solar radiation in the unshaded trees and that the temperature was higher, while the shade mesh reduced interception and solar radiation, reducing the temperature by 6°C. These findings highlight the potential of shade cloth to influence the budding and production of cherry trees, especially under conditions of high solar radiation.
On the other hand, results from Beppu and Kataoka (2000), where they experimented with different meshes, providing a lower and higher percentage of shade, demonstrated that shading reduced the maximum daily air temperature and that light reduction decreased the frequency of double pistils, and concluded with the possibility of applying artificial shading to reduce the appearance of double fruits or ovary malformations in cherry trees grown in regions with hot summers.
This is a technology system that helps an industry maintain a sustainable business over time, which can benefit large and small producers and agro-climatic areas with very interesting potential, that can be maintained in years of lower dormancy quality.
In addition to this, we must add the effects that a year with the influence of the child phenomenon implies; warm winters and cold springs, where it is uncertain to determine the periods under this phenomenon.
In conclusion, the combination of management strategies and the use of technologies such as shade nets are presented as essential tools to face cold deficiency, improve the dormancy stage and optimize cherry production in challenging climatic conditions, thus contributing to maintaining a sustainable business in the industry.
Beppu K, Kataoka I .(2000). Artificial shading reduces the occurrence of double pistils in ‘Satohnishiki’ sweet cherry. Scientia Horticulturae 83: 241-247.
Rodríguez M, Morales D. (2015). Shading nets effect on the production and quality of blueberry fruit (Vaccinium corymbosum L.) cv. Brigitta. Scientia Agropecuaria, 6(1), 41-50.
Ruiz, D., Egea, J., & Martínez‐Gómez, P. (2005). Effect of shading and paclobutrazol during dormancy on apricot (Prunus armeniaca) productivity. New Zealand Journal of Crop and Horticultural Science, 33(4), 399–406. doi:10.1080/01140671.2005.9514376
Valdebenito L. (2020). Effects of shade mesh and tent on apple tree (Malus domestica borkh) variety Scilate | ENVY®. Undergraduate reports Agronomy University of Talca.