Product applicationsPhytosanitary products, regardless of the applicator machines, must be given special attention, both by applicators and users of this application. Especially when referring to aerial application, some precautions must also be highlighted so that we have positive responses to the action of chemical or biological products and, therefore, we can benefit from all their phytosanitary characteristics.
A good application is a direct response to several factors, starting with the spraying itself, which corresponds to the generation of droplets produced with diameters appropriate to the needs of good coverage of the target and its absorption/retention capacity, the expected volume and the choice of best tip with the best features. The transfer of these particles generated during spraying constitutes what we call application, where meteorological factors, plant architecture, target positioning, plant health aspects, timing of application, among others are points that affect the final results.
Unlike terrestrial applications, where the bar is generally very close to the plant canopy, in aerial applications one should not fly extremely low (wheels touching the plantation), as in addition to causing irregular dispersion, the deposition bands will be uneven, causing distribution inadequate with a greater tendency for the product to concentrate in one of the “wings” of the aircraft (left wing) due to the displacement of air caused by the rotation of the propeller. Although there is movement of the plants due to the displacement of air in very low flights over the canopy of the plants, the aerodynamic effects favorable to good distribution will be compromised.
Another aspect to consider is the presence of humidity caused by dew. To apply or not to apply with dew is a very common question. The presence of dew may be beneficial to the redistribution of the product on the surface of the plant, however, its excess may cause runs, especially if the syrup (product and diluent - most commonly water) has not been added any adhesive additive, such as an adhesive spreader. .
In most phytosanitary product leaflets there are recommendations that applications be carried out at temperatures below 30ºC or 32ºC and with winds below 10km/h. For these parameters, the temperature conditions must be directly associated with the evaporating nature or not of the product, the size of the particles generated at the time of spraying and the direction of the wind, in order to avoid drift problems. However, meteorological factors should not be analyzed in isolation but rather as a whole.
An application equipment is considered calibrated when the flow variation between the desired flow rate obtained in theoretical calculations and that found in field conditions presents a nominal volume variation of 5% to those obtained in “theory”. These values, whenever possible, should be minimized for better use of the applied solution.
Worn spray tips, in addition to changing the applied volume, may compromise the quality of the drops generated, altering the desired droplet spectrum, resulting in a deficiency in the desired droplet patterns.
An increase in pressure above 25% for a given work situation changes the size of the drops generated and the increase in pressure results in greater flow. Small adjustments are allowed to achieve the desired flow rates. But for large changes aimed at obtaining a greater or lesser volume, it is recommended that the tip be changed to the required flow rate.
Actions such as maintenance of application equipment, to observe details of wear on the tips, carefully check possible leaks, physical damage to the equipment and carry out periodic cleaning are extremely important aspects in the preservation of the entire assembly and security for a correct and safe application. decontamination of the tank, bars and filters.
When we refer to choosing the appropriate tips to be used for an application, we see that there is currently a very wide range of tip options produced by the most different manufacturers. They are tips with excellent manufacturing quality and that meet the desired volume and droplet size needs, with metallic or synthetic materials. The choice of any tip or application method must always take into account factors not only of volume, but observing the type of droplet desired, the spectrum of drops produced by that equipment or tip and the nature of the product applied.
The adoption of products that promote changes in viscosity and droplet size has been a suitable option when it is necessary to manage factors external to the spraying process. This provides greater operational dynamics for solving adverse situations, such as the addition of products to minimize drift in risky conditions or to improve the deposition performance of certain products.
Care in adding these products, their proportions, mixing sequence, possible changes in flow rates and changes in coverage densities and physical-chemical aspects should be a matter of special attention.
Application ranges are another aspect that also deserves great attention. In aerial applications, the different passages that will provide coverage due to overlaps are monitored by pilots through the guidance generated by the DGPS lightbar. During the passage of the aircraft, the total application range represents the range where particles (solid or liquid) are present, regardless of the distribution quality. In order to have the appropriate coverage with uniformity, the technician responsible carries out overlapping and distribution identification studies and, thus, identifies and determines the effective operational application range, which is the range obtained with different passes at pre-established distances and which will provide the best deposition quality with overlaps, maintaining uniformity across the entire extent of the applied area.
For this, the coefficient of variation (CV%) values between passes are determined, that is, in the effective operational deposition range, often simply called the application range. When the total application range presents a normal distribution, the effects of side wind (crosswind), headwind or tailwind are minimized and, therefore, applications carried out, either in the “carousel” guidance system, made with passes in the same direction , or through the “BK-BK" (back and forth) system, will present similar deposition quality responses.
Therefore, the choice of application modality, land or aerial, is the producer's option, but aerial applications have certainly received a lot of attention from their operators in order to provide deposition quality, quickly and safely, through training. , recycling and incorporation of advanced technical monitoring technology. In this sense, a quality certification program is being implemented with the support of Andef and Sindag called the CAS Project (Sustainable Aeroagricultural Certification), coordinated by professors specializing in application technology from the universities Unesp, UFU and Ufla, which will soon bring significant improvements for every application, allowing producers to have quality references among operating companies.
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BASIC CARE IN AERIAL SPRAYING
Agricultural aviation companies, providers of specialized air services (SAE), must have their documentation regularized, with qualified and regulated professionals (Anac and Mapa) by bodies responsible for aeronautical and agricultural inspection, respectively.
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