Vortex spray system

Comparative studies show that sprayers with air assistance on the boom have higher efficiency than conventional ones, in evaluations carried out at the same speed, plant height and tank volume.

The search for new technologies for applying chemical products to obtain better levels of product efficiency on the target is directly related to the quality of application. The study of deposition, coverage and drift acts as an influential factor in efficiency, responsible for losses, with drift being a factor in environmental contamination.

Several commercially important plants are attacked by diseases and pests that start in the lower third of the plant's structure, making initial control difficult. Sprayers with air assistance on the boom have become a good alternative for controlling diseases that begin attacking in the lowest part of plants, such as Asian soybean rust, caused by the fungus Phakopsora pachyrhizi, which causes a large drop in production or even the loss of the crop when not managed properly.

Several commonly applied phytosanitary products have locosystemic action, that is, they are translocated at small distances within the plant and therefore require, during application, greater coverage of the plant to obtain greater efficiency, making air assistance in the bar a major ally in increasing the quality of application, reaching the lower canopy of the crop. The liquid, after leaving the spray tip orifice, loses energy due to air resistance, which makes it easier for these drops to be carried by the wind, causing the product to drift. When using air assistance on the boom, these droplets are carried by a downward air current that facilitates the guidance of the droplets to the chosen target, reducing product drift.

The system for applying chemical pesticides with air assistance next to the spray bar is recommended for tall crops with high leaf density, due to greater penetration into the crop canopy. Its advantages are less dependence on ambient wind, higher application speed, greater coverage in the crop canopy, allows the use of fine drops, reduced application volume, reducing product costs and shorter downtime for supply and especially reduction of drift, contributing to less contamination of the environment. Reducing drift becomes very important when you are concerned with preserving areas around the property, as a product applied to a crop can be very harmful if it comes into contact with another area, especially when it comes to herbicides.

On bare soil or with plants in the initial stages of development, the use of air assistance is not recommended, as it increases the drift caused by the deflection of air caused by the sprayer through the soil. The umbrella effect in the crop, in which the lower parts of the plant and between rows are covered by leaves, reducing product deposition in these areas, is prevented due to the turbulence generated by the air curtain, allowing greater efficiencies in product deposition over the target.

Research conducted comparing the use of air assistance in the boom with conventional sprayers proves the efficiency of air-equipped equipment in the deposition and losses of chemicals using artificial targets, revealing significantly lower levels of drift compared to conventional equipment. Higher wind speeds near the bar provide greater coverage and consequent control of pests and invaders, compared to lower air speeds. In the work conducted by Miranda et al (2011), the authors concluded that spraying with air assistance at the boom can increase target coverage by the droplet, especially on more difficult targets such as the middle and lower positions of the plant and the undersides of cotton leaves. According to the authors, air assistance favored the application by minimizing the effects of climatic variables, carrying the drops more quickly to the target.

Sprayers equipped with air assistance near the spray bar can be trailed, mounted or in some cases self-propelled. They consist of one or two hydraulically driven fans, generally arranged axially, positioned close to the central section of the spray bar. These fans have the function of producing a large volume air curtain and distributing the air flow over the spray bar mounted above the nozzles through an inflated duct. The air generated and distributed in the duct above the bar is forced to pass through the opening in the perpendicular direction from which it was generated, in a downward direction, leading the sprayed volume through the tips to the target.

Sprayers typically use a fan to produce the air curtain. This fan is driven by a hydraulic motor driven by the tractor's TDP or by the independent remote control system. The fan rotation variation is carried out through a regulating valve, which, when its position is changed, varies the flow of oil to drive the hydraulic motor, thus changing the fan rotation and the amount of air admitted into the system, according to the application need. The power consumption for activating this air system increases as the fan speed increases.

In order to increase deposition and reduce soil contamination, varying the angle of the nozzles and/or air generated by the system during spraying in favor of the direction of travel of the tractor-sprayer can be a good alternative, ranging from zero to 30 degrees in relation to the vertical (Table 1).

The disadvantages of the assisted spraying system are higher costs in purchasing the product, possible dragging of spray droplets onto the upper part of the leaves and, in some cases, falling flowers, being more suitable for fungi and pests that initiate the attack. in the lower part of the plants.

It is worth mentioning that the use of air assistance can reduce or increase product drift when compared to a conventional sprayer, and it is extremely important to analyze the target crop for application and the plant's development stage, performing the interaction of these factors with the air speed at the spray bar and the type of nozzle used.

Studies for comparative purposes have shown that sprayers with air assistance on the boom have higher efficiency than conventional ones. In evaluations carried out at the same speed, plant height and tank volume, the deposition of drops on soybean leaves in the conventional system presented average values ​​much lower than those in the Vortex system.

Another important fact refers to the increase in the number of hours that can be worked in a day. Data from manufacturers indicate that the system can assist in applications where the wind would become an impediment, causing a large amount of drift. In this sense, the air-assisted spraying system is an alternative to minimize losses of phytosanitary product due to drift and increase application coverage, especially in the lower layers of the crop canopy. Work has been carried out to measure the relationship between the vegetative density of the crop and its real relationship with stepwise increases in wind speed near the spray bar for better application.

Bruna Batistella, Camila Dalcin, Bruno Bisognin, Tiago Lopes, Alcionei Dallaporta, Vilnei Dias, Lamap/Unipampa Alegrete

Article published in issue 156 of Cultivar Máquinas.