By: Raúl Osorio, Director of Peulla Consulting and Services.
«This season there will be more fruit, less labor, more phytosanitary control, a somewhat uncertain maritime transport panorama, but that should not make us impatient if we have the peace of mind of having fulfilled our obligations in the field.«. (Source: Avium Phonological Report, Season 2021-22, November 5, 2021)
In the Pre-Harvest stage, a series of applications are developed aimed at controlling key pests and diseases in cherry trees, for example, control of Drosophila suzukii, Botrytis cinerea. Exogenous applications of gibberellic acid of the AG3 type are also developed after the straw-yellow colour stage (stage III/beginning of veraison), which increase the size and hardness of the fruit. (Source: Smartcherry “Gibberellic acid in cherry production: theoretical bases and experiences in Chile”).
Other applications are aimed at improving the condition and quality of the fruit and organs, such as the shelf life of the pedicels, among other quality factors.
There is also the use of different solutions to avoid fruit cracking that occurs due to rainfall events prior to harvest.
All of them applied in a mixture or alone depending on the available formulations and their mixing compatibility.
Once again, and as in the previous articles, it is very important for advisors, researchers and producers:
- Consider the correct application of the products, as well as the calibration of the machinery used to perform these applications.
- A calibrated machine, with adequate pressure and operation, nozzles in good condition, etc. allows the application of any product to be effective (Carlos Tapia).
We have already reviewed in the previous post, that it is vital that:
- Preventive maintenance is carried out on each of the available equipment (atomizers and tractors).
- 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 (fruits, leaf tissue and wood)
c)Volume of air needed to move the applications
d)Speed of advance of applications in the field to achieve good coverage or amount of deposit on the target (fruit, leaf tissue and wood).
We will use the same methodology described in the previous articles to determine the application requirements in the pre-harvest stage of cherry trees.
Volume of water: We must always consider that our objective is to achieve good “drop coverage” on the organs of our crop, which in turn will depend on: “the height, size or volume of the canopy.”
One way to calculate the volume of water to be used is by determining the crop volume through TRV (Tree Row Volume) or Tree Volume. TRV (m3 of tree/ha) = [height of tree from first branches (m) x average width of tree (m) x 10,000 (m2/ha)] / Distance between rows (m).
The size of the trees at this stage of cultivation (pre-harvest) is very similar in most cherry orchards and will vary depending on the training systems.
As an example, we will consider a garden with the following measurements:
Average tree height from first branch: 2.7 meters (3.2 meters total)
Average tree width: 2.5 meters
Planting distance: 4.0 meters
The TRV = (2.7 x 2.5 x 10,000) / 4.0
The result will be TRV = 16.875 m3 of objective.
To obtain the volume of water to use Byers et.al They represent a volume of 0.0936 L/m3 canopy with foliage.
For our example, therefore, we would need 16,875 x 0.0936 = 1579.5 L of water / ha.
However, we only need 80 % of this calculated volume for applications targeting well-pruned trees, adequate light in the tree, vigorous shoots on main branches, plenty of space in the foliage to allow light to pass through. This calculation is cited by the Agricultural Engineer Guillermo Lorca Beltran 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 0,8 (Well pruned), it throws a volume of water to be applied of 1260 L of water/ha.
Volume of air to be displaced in pre-harvest applications:
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 with an average height of 2.7 meters, with a “branch” width of 2.5 meters and a planting distance of 4.0 meters.
The TRV = (2.7 x 2.5 x 10,000) / 4.0.
The result will be TRV = 16,875 m3 x 0.8 = 13,500 target (fruits and plant tissue in pre-harvest).
This calculated volume is what we must move to reach our objectives.
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 (13,500 m3 in the example) we must consider:
- The speed of progress of the application
- Adjustment of the air group multiplier box
- Adjusting the blades to the required position or inclination.
- Adjusting the working RPM.
For our example, we will consider a forward speed of 6.5 km/hour in an orchard with a distance of 4.0 meters between rows and an air output speed from the equipment's air group of 16 m/sec:
| D. Plantation | km/hour | Time/ha (min) | m3 of air/ha |
| 4 | 6,5 | 23,08 | 13646,8 |
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.
We will choose nozzles that produce medium to small droplets to generate good deposit on the targets (good amount of drops/cm2).
In order to develop effective and efficient application management plans, we must have equipment previously diagnosed 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..
