«The great desire of every producer is undoubtedly to advance their harvest and improve their productive potential of their orchard and that this translates into a better profitability of their business. Dormancy breakers (DR) continue and will continue to be the subject of study for researchers and extension agents, who are constantly trying to replicate different strategies in cherry orchards that can advance or homogenize the initial phenological states (flowering and sprouting), and translate them into the advancement or homogenization of the harvest. However, it is necessary to be clear about when and when to use hydrogen cyanamide or a dormancy breaker.«. (https://cutt.ly/imHSnWH)

For the advisors and researchers cited in the same publication, it is very important:

• A correct application of the products must be considered, as well as the calibration of the machinery with which said applications are made. A clear example of an error is making an application outside of doses, with a high concentration or excessive wetting, which can generate phytotoxicity or damage to the wood and floral primordia. It is important to take into account that dormancy breakers are not worked in doses per ha, but in concentration or percentage: for example 2 liters in 100 liters of water (2%), 3 liters in 100 liters of water (3%), etc.
• Regarding the machines, it is estimated that 90% of the machines that are used in Chile to apply agricultural products present some calibration problem, a situation that must be resolved urgently because the effectiveness of the products, in this In the case of Hydrogen Cyanamide, or Dormancy Breakers (DR), it depends 50% on its application, together with its correct dose.
• A calibrated machine, with adequate pressure and gear, nozzles in good condition, etc. allows the application of any product to be increasing. It must not be forgotten that these products (Cyanamide and RD) act by contact, therefore, they require water like Carrier, and a well calibrated machine will arrive with the products in a homogeneous and correct way to all sectors of the tree, especially to the highest part (https://cutt.ly/imHSnWH).

We have already reviewed in the publication the important factors to consider for winter applications, it is vital that:

• Preventive maintenance is carried out on each of the available equipment (sprayers and tractors).
• Have precise and appropriate calibration guidelines for each orchard situation according to topography, orchard age and driving system.

To develop a proper calibration to run these applications we must consider:

• Volume of water to use
• Volume of canopy to treat (darts and buds in wood)
• Volume of air required to displace applications
• Advance speed of field applications to achieve good coverage or amount of deposit on the target (darts and buds on wood).

Volume of water: We must always consider that our objective is to achieve a good “coverage of drops” in the organs of our crop (darts and buds) which in turn will depend on: “the height, size or volume of canopy” or “volume of structures”.

One way to calculate the volume of water to use is by determining the volume of the crop through TRV (Tree Row Volume) or Tree Volume. TRV (m3 of tree/ha) = [height of the tree from the first branches (m) x average width of the tree (m) x 10,000 (m2/ha)] / Distance between rows (m).

The dimension of the trees at this stage of the crop (recess) is very similar in most cherry orchards and will vary depending on the training systems.

Just as an example we will consider an orchard with the following measures:

-Average tree height from the first branch: 2.7 meters (3.2 meters total)

-Average tree width: 2.5 meters

-Planting distance: 4.3 meters

-The TRV = (2.7 x 2.5 x 10,000) / 4.3

-The result will be TRV = 15,697.7 m3 of objective.

To obtain the volume of water to useByers et.al assume a volume of 0.0936 L/m3 of canopy with foliage.

For our example, therefore, we would need 15,697.7 x 0.0936= 1469.3 L of water / ha.

However, and according to the publication of the advisors cited in this article (https://cutt.ly/imHSnWH); we only need 70% of this calculated volume for applications directed at darts or buds in wood; this calculation is also cited by Ing. Agr. Guillermo Lorca Beltrán Professor of Agricultural Mechanization of the Faculty of Agronomy and Forestry Engineering, PUC of Chile glorcabeltran@hotmail.com, in his article EXACTITUDE SIN APURO of the Mundo Agro magazine, a foliar density adjustment index should be applied.

If we apply the factor 0.7 (extremely open), it gives us a volume of water to apply of 1028.5 L of water / ha.

After several years of experience and applications in the field, and checking the deposits with hydrosensitive paper, fluorescent paints and also kaolinites for agricultural use, seeking that the deposit of drops (coverage) does NOT generate excesses or drips, we can apply the factor of 0 .75 to this calculation.

Therefore, and for the example and based on field experience, the adjustment recommendation for applications intended for tips and darts in wood:

1028.5 L x 0.75 = 720 L of water / ha.

Field verification with kaolinite.

Volume of air to displace in winter applications: Another very important factor to consider is the volume of air necessary to displace our application towards the objective.

One way to calculate the volume of air needed is also by determining the volume of the crop 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 with an average height of 3.2 meters, with a width of “branches” of 2.5 meters and a planting distance of 4.3 meters.

The TRV = (3.2 x 2.5 x 10,000) / 4.3. The result will be TRV = 18.605 m3 x 0.7 = 13.0.23 target (wood).

This calculated volume is what we must move to reach our objective “Wood”.

The air-assisted hydropneumatic equipment that is the most used in our fruit growing has different air displacement capacities depending on its model and type of air group.

The different models existing in the country generate amounts ranging from 25,000 to 90,000 m3 of air / hour. To adjust the amount of air / ha (13.023 m3 in the example) we must consider:

• The speed of progress of the application
• Adjustment of the multiplier box of the air groups
• Adjustment of the blades in the necessary position or inclination.
• Adjustment of the work RPM.

For our example we will consider the following forward speed chart in an orchard with a 4.3 meter distance between rows:

To achieve a better level of deposits, it is always recommended to use the lowest speed possible, considering the operational capacity of the spray equipment in the field. (https://www.redalyc.org/pdf/932/93215307.pdf)

Choice of Nozzles: The cleanliness of these components must always be maintained and the flow rate they deliver per minute should be checked and that it is the one indicated by the manufacturer, not exceeding 10% wear.

For the example:

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 result in the success of our cultivation to harvest with the least impact to the environment and people.