By: Raúl Osorio, Director of Peulla Consulting and Services.
Pollination is the fundamental process for the reproduction and production of any crop. In the case of cherry trees, although they have a very short flowering period, the most important milestones for the formation of seeds and the initial growth of the fruit occur in just a few days, which will define the productive potential of an orchard during the season.
Once the ovules have been fertilized, the process known as fruit setting begins and the plant waits to complete its three stages of development: cell division, hardening of the stone and cell elongation. These three processes develop independently and require different nutritional and hormonal needs within the plant, considering that there are cultural tasks that will enhance each of these processes with the aim of achieving maximum productive potential.
In turn, between the flowering and fruit set stages, a series of applications are developed aimed at controlling key pests and diseases in cherry trees, as well as foliar correctors or nutrition, growth regulators, promoters of plant defense mechanisms, among others. All of them applied in a mixture or alone, depending on the available formulations and their mixture compatibility.
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.
- As for the machines, it is estimated that 90% of them used in Chile to apply agricultural products have some calibration problem, a situation that must be resolved urgently, since the effectiveness of the products depends 50% on their application, together with their correct dosage.
- 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 (flowers, leaf tissue at the beginning of budding 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 (flowers, leaf tissue and wood).
Volume of water: We must always consider that our objective is to achieve good “drop coverage” on the organs of our crop (flowers, leaf tissue and wood), which in turn will depend on: “the height, size or volume of the 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 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 the crop (flowering to fruit set) is very similar in most cherry orchards and will vary depending on the training systems.
Just 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 m 3 of target.
To obtain the volume of water to be used, Byers et.al. assume a volume of 0.0936 L/m3 of 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 70 % of this calculated volume for applications directed to flowers and initial leaf tissue. This calculation is also cited by 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 MundoAgro, who points out that a leaf density adjustment index should be applied.
If we apply factor 0.7 (extremely open) it gives us a volume of water to apply of 1105.65 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 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 “branch” width of 2.5 meters and a planting distance of 4.0 meters.
The TRV = (3.2 x 2.5 x 10,000) / 4.0.
The result will be TRV = 20,000 m 3 x 0.7 = 14,000 target (flowers and plant tissue at the beginning of sprouting).
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 quantity of air/ha (14,000 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:
Choice of Nozzles: These components must always be kept clean and the flow rate they deliver per minute must be checked, and verify that it is as indicated by the manufacturer, not exceeding 10 % of wear.
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.
