By: Raúl Osorio, Director of Peulla Consulting and Services.
Some physiological considerations of winter recess in cherry trees:
Deciduous fruit trees shed their leaves and cease visible growth as a strategy to survive the cold winters, with their buds entering a state of dormancy, through a process known as winter recess. The entry into this phase is gradual and begins with the shortening of the days in summer. Then, as autumn progresses, with shorter and colder days, the tree accumulates growth inhibitors that induce the fall of the leaves, a moment that signals the beginning of the state of deep dormancy or endo-dormancy. After a period of exposure to winter conditions: low temperatures, rain, low luminosity and photoperiod, the bud reaches a state called eco-dormancy, in which it is ready to sprout and continue its cycle, which will occur according to the increase in temperature and greater luminosity of the days in spring. Source: Agricultural Network, September 2020 “Considerations on the recess in fruit trees” Fruit Ecophysiology Laboratory. Álvaro Sepúlveda ([email protected]). Loreto Arenas ([email protected]).
With the beginning of the leaf fall process of the crop, the application of solutions focused on disease control begins, such as: Bacterial cancer, Cytospora and wood diseases. https://smartcherry.cl/poscosecha/recta-final-para-la-entrada-en-
dormancy-of-cherry-orchards.
To develop applications aimed at controlling the diseases mentioned in this period, we must consider:
- The objective of the applications during this period is focused on covering the wood of the crop and especially the natural wounds caused by falling leaves, wounds and micro wounds caused by frost and eventual hail, where the described pathogens can enter.
- Second: carry out preventive maintenance on each of the available equipment (atomizers and tractors).
- Third: have precise calibration guidelines appropriate to each orchard situation according to topography, orchard age and conduction system.
To develop a proper calibration to run these applications we must consider:
a) Volume of water to be used
b) Volume of canopy to be treated (with or without foliage)
c) Volume of air needed to move the applications
d) Speed of advance of the applications in the field to achieve good coverage or amount of deposit on the target (wood).
Volume of water: There are many recommendations regarding the amount of water to use for applying phytosanitary solutions; however, we must always consider that our objective is to achieve good “drop coverage” on the organs of our crop, which experiences changes in “height” or “canopy volume” or “structure volume” and “losses” of organs such as leaves.
One way to calculate the volume of water to be used is by determining the crop volume through TRV (Tree Row Volume) or Tree Canopy Volume. TRV (m3 of foliage/ha) = [tree height (m) x tree width (m) x 10,000 (m2/ha)] / Distance between rows (m).
The size of the trees at this stage of cultivation is very similar in most cases and will depend on the training systems. Just as an example, we will consider an orchard with an average height of 3.2 metres, with a “branch” width of 3 metres and a planting distance of 4.0 metres. The TRV = (3.0 x 3.0 x 10,000) / 4.0. The result will be TRV = 22,500 m3 of target.
To obtain the volume of water to be used, Byers et.al assume a volume of 0.0937 L/m3 of canopy. For our example, therefore, we would need 24,000 x 0.0937= 2108 L of water/ha.
According to Agr. Eng. Guillermo Lorca Beltrán, Professor of Agricultural Mechanization at the Faculty of Agronomy and Forestry Engineering, PUC of Chile [email protected], in his article ACCURACY WITHOUT HASTE in the magazine Mundo Agro, a leaf density adjustment index should be applied.
If we apply the factor 0,7 (extremely open) gives us a volume of water to apply of 1476 L of water/ha.
However, this information refers to fruit crops with foliage. When determining the volume of water needed to apply to the crop WITHOUT leaves, we must adjust this volume to factors determined only by years of experience in the field and corroborating the deposits with hydrosensitive paper and other means such as fluorescent paints and also kaolinites for agricultural use.
Therefore, after what has been explained above and based on field experience, the adjustment recommendation for applications intended for wood, we must adjust the result by the same factor of 0.7 for trees without leaves. For the purposes of the example we have 1476 L x 0.7 = 1033 L of water / ha.
Another way to calculate is to consider the use of 400 L of water for every 10,000 m3 of canopy, for the example we have (24,000 m3 / 10,000 m3) / 400 L = 960 L of water/ha.
Volume of air to be displaced in winter applications: Another very important factor to consider is the volume of air needed to move our application toward the target.
One way to calculate the air volume needed is also to determine the crop volume through TRV (Tree Row Volume) or Tree Canopy Volume. TRV (m3 of foliage/ha) = [tree height (m) x tree width (m) x 10,000 (m2/ha)] / Distance between rows (m).
For the same example above, an orchard of average height 3.2 meters, with a “branch” width of 3 meters and a planting distance of 4.0 meters. The TRV = (3.0 x 3.0 x 10,000) / 4.0. The result will be TRV = 22,500 m 3 x 0.7 = 15,750 of target (wood).
This calculated volume is what we must move to reach our objective “Wood”.
The hydropneumatic equipment with air assistance, which is the most commonly used in our fruit growing industry, has different air displacement capacities depending on its model and type of air group.
The different models existing in the country generate quantities ranging from 25,000 to 90,000 m3 of air/hour. To adjust the amount of air/ha (15,750 m 3 In the example) we must consider the progress speed of the application.
For our example we will consider the following table of forward speeds in an orchard with a distance of 4.0 meters between rows:
lowest possible, considering the operational capacity of the atomizing equipment in the field.
Choice of Nozzles: These components must always be kept clean and the flow rate they deliver per minute must be checked and verified to be as indicated by the manufacturer, not exceeding 10 % of wear.
To improve the application of solutions during leaf fall and winter periods, it is recommended to use Anti-Drift nozzles and adjust their number and arrangement to the crop architecture and its various conduction formats.
The working pressure for the applications must be in an optimal range between 8 and 14 bars both at the equipment command and at the nozzle outlet.
For example:
In each case we must always “consistently achieve high efficacy with the necessary amount of product and at a sustainable cost and always with minimal impact on the environment, applicators and consumers.”
In order to develop effective and efficient application management plans, we must have previously diagnosed equipment in all its components, repaired and replaced its critical elements, perform annual and periodic maintenance, permanent cleaning and have highly trained personnel to develop the applications that will translate into the success of our crop at harvest with the least impact on the environment and people.
