A tractor and a sprayer that work in perfect harmony and agreement. To make a correct application we will have to make several decisions to select the regulation of the components of the collar.
Concordance and sprayer
Long before applying, at the time of purchase, we must ensure that the tractor is for the terrain and soil we have and that the power is sufficient to move (on flat and firm terrain, 15% of the tractor's power), drag the equipment and the liters of water plus product it carries, move the pump, from 5 to 15 HP and operate the fan, which can be a power requirement of over 40 HP.
The spraying equipment, on the other hand, will be subject to the tractor's capabilities, in terms of the air unit; a high-flow air unit allows me to advance faster, but it consumes more fuel and tractor power. The tank is heavy, therefore, the tractor's power and the topography of the terrain, in addition to the equipment's track, are important factors to consider. As for the pump, the volume of application per hectare and the forward speed will determine the flow rate we need and we have to allow 30% of the capacity for agitation and losses in the system.
Ground speed, RPM, range and gear
The quality of the application is seriously affected by the speed, sprayers make the droplets travel by means of air (those with this implement). The faster we go, the drops are left behind when they leave the equipment, for this the fan pushes them; the more air, the farther it throws them, but as big as the fan is, the terrain and the operator's skills will be another limitation and the literature speaks of a limit of 6 km/HR (ambient wind conditions can make this value much smaller). A slow application speed will give us quality of application, but the efficiency of the time resource disappears.
When we make the decision of how fast we go, we are faced with another regulation decision. A tractor can go at the same speed in different gears, in addition to the combination with a range (for example, a tractor with high and low range, plus 1st to 5th gear). The determining factor here is the pump, since these cannot, in general, work at more than 540 RPM, value in which, in addition, the flow and pressure measurements are made. The lowest limit at which we can work them is 400 RPM. The work can be at any point between these two values of revolutions of the PTO, noting that the flow of the pump will be lower than the factory nominal, as well as the air generated by the fan.
Each tractor manufacturer indicates at what engine revolutions it will deliver the 540 in the power take-off, with some having the option of normal and economical ones for implements requiring less than 30 HP.
Pressure and nozzles
The working pressure will depend on the type of nozzle and the flow rate we need to reach the desired volume to be applied per hectare. The most commonly used nozzles for cherry trees are the disc cone and diffuser type, where most manufacturers of these models recommend their use from 5 to 20 bar, with an optimum of 8 to 15 bar. Here it is very common to find fields where the equipment arrives with a type of nozzle and they adapt the applications to those nozzles and we must select the nozzles that we really need. The amount of foliage on the trees is not uniform and the drops travel more to the upper part, therefore the nozzles should not all be the same, that is, of the same flow rate, having a model in which the lower half of the nozzles delivers the 33% of the application and the upper half the remaining 66% (this is one of the models described, there may be other configurations suggested in the literature).
Fan
The fan can have a multiplier box that takes the RPM from the power take-off and leaves it disengaged, that is, 0 revolutions, for when we are, for example, returning from loading product with the pump running and to operate the agitator and not raise dust when moving; but when we get to the area to apply, we place it engaged.
There are machines that have two multiplication positions, for example, the TDFx3.5 or the TDFx4.5; which one will we use? It depends on the amount of air we need. We can do this visually, evaluating how many rows, in addition to the applied one, we are covering. If we reach 2 rows beyond the applied one, we are generating more air, with the cost in fuel and the loss of product; if we reach just halfway up the tree in the row, it sounds good, but we must consider that ideal conditions are not always present, therefore, covering up to half of the next row is not so excessive, nor so close together. The angle of the blades can also be adjusted in some fans.
Not all trees are the same, the year of planting, the vigor, the formation, the pruning, the foliage according to phenological state, therefore, just as the volume to cover the plant changes, the amount of air used also.
Everything described above must be considered before purchasing the equipment so as not to fall short. During the development of the plants, the regulations will change, seeking Quality, Efficiency and Sustainability in its 3 dimensions.
To complete the procedure and be certain that each selected parameter is correct, we must verify with hydrosensitive papers, seeking uniformity in the plant profile with minimal impacts to achieve the biological objective of the application.
