By Raúl Osorio – Director of Peulla Consulting and Services SPA
It is a general consensus among the main advisors and producers of cherries that “the next season of growth and production of the crop begins in post-harvest”. It is also the occasion for a series of applications focused on maintaining the optimal physiological status of the crop, such as: use of sunscreens, foliar fertilization and applications for pests that are difficult to control such as phytophagous spider mites, San Jose scale and other pests present in the crop.
Subsequently, together with the beginning of the leaf fall process of the crop, the application of solutions focused on the control of bacterial cancer and wood diseases begins.
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.”
It is at this point, therefore, that we must develop a rigorous inspection protocol for the machinery intended for the applications of each of these solutions and carry out preventive maintenance on each of the available equipment (sprayers and tractors). Once the maintenance has been carried out, we must have precise calibration guidelines appropriate to each orchard situation according to topography, age of the orchard, driving system, among others.
Pesticide application is one of the most important practices in fruit and vegetable production worldwide. In some cases it represents more than 50 percent of the machinery used in an orchard in one season. (Source: Jorge Riquelme S. and Patricio Abarca R. INIA Information Booklet No. 1).
Maintenance of agricultural spray equipment:
This time we will refer to the different components of an agricultural sprayer and the preventive maintenance and periodicity of control. An illustrative sheet of them is attached.
Hydraulic pump: Maintenance of this hydraulic component must be carried out once a season and its inspection must be permanent, considering the working condition of the pump, oil level and pressure of the device. During annual maintenance, membranes or sleeves and pistons must be replaced or repaired depending on the model and hydraulic system.
Gimbal and gimbal sheath: The maintenance of this safety component must be carried out once a season and its inspection must be permanent, considering the condition of the cardan sheath and that it maintains its anti-rotation elements (holding chains). The lubrication of this mobile component must be carried out daily.
Command: The maintenance of this hydraulic component must be carried out once per season and its inspection must be permanent, considering the condition of the pressure regulating valve, air outlet distributor, sector opening and the pressure gauge, which ideally has a 1 in 1 isometric bar scale.
It is very important to check the working pressure at the nozzle outlet to determine the proper functioning of the control or to “adjust” the pressure in the field.
Filters: These components must be cleaned regularly and in every application. There are: filling mouth filter, main or suction filter, nozzle filters and in-line filters.
Pond and its components: The cleaning maintenance of this hydraulic component must be carried out permanently and after each application. Additionally, it is recommended to carry out the permanent maintenance and cleaning of the tank drain plug. One component of the tank is the level hoses that must be visible, translucent and with a level sight glass. Another component of the tank is the cover(s), which must be in perfect condition along with their pressure retaining valves; they must also close easily. If they have a clean water tank, it must be in perfect condition with a cover and key to fulfill its function as a safety element.
Pipes and hoses: The hoses must be checked for leaks or punctures and it is therefore always recommended to keep them routed through the chassis of the equipment. The cleaning maintenance of these hydraulic components must be carried out permanently and after each application. It is recommended to develop a cleaning schedule with detergents and specific cleaning products at least 3 times a season and ideally 5 times when we use products that are difficult to dissolve and also products in mixtures.
Air group: This component must be serviced once a season, verifying the proper functioning of the gearbox in its high, low and neutral positions. The good condition of the blades and their angle adjustment of the fan group must be verified. The protective grid of the air group must be permanently checked, since it is a very important safety element for applicators. If the equipment has deflectors in the air group, their good maintenance condition and position must be permanently verified.
Nozzles: The maintenance of these components consists of permanently checking their cleanliness, ideally before each “round” of applications. To verify the proper functioning of the nozzles, the flow rate they deliver per minute must be checked and it must be verified that it is the one indicated by the manufacturer at a given pressure (tests at 10 bar are recommended). If the detected flow rate is greater than 10 percent of that indicated by the manufacturer at 10 bar, the nozzles with this defect must be replaced.
Nozzle flow measurement:
It is always recommended to have nozzle bodies with a “drop-stop” system to avoid leaks and contamination. It is recommended to develop a cleaning schedule with detergents and specific cleaning products at least 3 times a season and ideally 5 when we use products that are difficult to dissolve and also products in mixtures.
Stirring system: The verification of the proper functioning of this hydraulic component must be carried out permanently before each “round” of application.
Calibration of agricultural spray equipment
After checking or diagnosing the components of the atomizing equipment and implementing repairs, improvements, cleaning and annual or periodic maintenance; we can count on equipment that meets the applications that are necessary for our crop with the greatest accuracy. In this way we can achieve effective and efficient results from solutions applied to our crop.
It is of utmost importance that the personnel who operate and receive application instructions are highly trained to carry out each application and protected.
Personnel with personal protective equipment (PPE) and trained: Every sprayer operator must keep their personal protective equipment in good condition and replace it whenever necessary during the season. Always check.
The training, qualification and permanent accreditation of operators (applicators) must be permanent; the human factor is essential when it comes to a good application. The people who apply/dose must be trained, ideally have the SAG credential that accredits their competence. It is the applicator who must carry out the recommendations of a “calibrated application”, therefore, it will ultimately depend on him that the spraying is as efficient and effective as desired. In this way, the operator of the machinery must respect the selected gear, the engine revolutions, the working pressure, the cleaning of the nozzles and the maintenance of the use of the different components that directly interfere with the application.
Basic concepts for achieving a well-calibrated application in the field: The parameters that must be considered to achieve an optimal calibration pattern are: Working speed expressed in km/hour, working RPM of the engine transmitted to the power take-off, working pressure, type and number of nozzles. In addition, always consider the cleaning of the nozzles and the maintenance of the components that directly interfere with the application such as filters in general.
Working speed: To determine the working speed, the time taken (expressed in seconds) to cover a known distance (50 meters) must be determined. This work must be carried out on the ground between rows of crops to have the real working conditions of the application equipment. For this test, the nozzles, air group and agitation must be kept in operation. Speed tests will be carried out as many times as necessary according to the requirements of each orchard and the operability given by the number of spraying equipment existing for the total surface to be assisted.
To obtain the speed in km/hour, we must divide the distance (meters) by the seconds it takes to travel them and multiply this result by 3.6:
Time traveled per ha: To determine the time it will take our equipment in optimal conditions to cover 1 ha, we must consider the planting distance of our orchards expressed in kilometers. For example, the distances to cover in 1 ha for different distances between rows in cherry orchards:
| Distance between rows (meters) | Distance traveled (km) |
| 3,8 | 2,63 |
| 4 | 2,50 |
| 4,5 | 2,22 |
| 5 | 2,00 |
Once the distance traveled per ha expressed in km is known, we can calculate the time taken by multiplying the distance traveled per ha (km) by 60 and dividing this result by the speed obtained on the ground (km/hour).
Choice of nozzles (type and number): To choose the type and number of nozzles to use in an application of a recommended volume of water, we must consider the travel time per hectare of our equipment and choose the type of nozzle to use and the number of these to assist our crop depending on the volume of canopy it has. For example, if we have an orchard with a planting distance of 4 meters between rows and our equipment develops a speed of 5.5 km/hour:
Distance between rows (meters): 4
Distance traveled / ha (km): 2.5
Speed (km/h): 5.5
The time required to carry out a treatment in a cherry orchard planted 4 metres apart between rows is 27.27 minutes.
If our garden is “adult” or already in production, its height can vary between 2.8 and 3.2 meters, therefore, to assist a standard application of 1000 L/ha, we must divide this volume by the time spent on the application: 1000 L / 27.27 minutes = 36.67 L/minute.
This result tells us the flow rate per minute that we must have at the outlet of all the nozzles that we will choose, whether in type, number and working pressure, ideally between 8 and 16 working bars. Continuing with the same example for a device that has 14 total nozzle outlets, we must choose nozzles that deliver: 36.67 / 14 = 2.62 L/minute. Then we have the catalogs of nozzles existing on the market, such as: ATR empty cone, ATF full cone, TVI empty cone anti-drift, among others.
For example:
| Nozzle model | Pressure (bar) | Flow rate (L/min) | Time/ha | No. Nozzles | Final flow rate / ha |
| ATR Black | 9 | 2,64 | 27,27 | 14 | 1007,9 |
| Red ATF | 8 | 2,61 | 27,27 | 14 | 996,4 |
| Red TV | 8 | 2,61 | 27,27 | 14 | 996,4 |
The type of nozzles we should choose depends on the field conditions and the development stage of our crop, for example, if we have to apply foliage we can choose ATR or ATF nozzle models. If we have areas with high wind speed conditions (over 10 km/hour) we can choose anti-drift TVI nozzles.
For leafless growing conditions and wood-focused applications such as winter coppers for leaf control. Pseudomonas, or bacterial cancer we can choose TVI anti-drift nozzles.
Conclusions: 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.
