Spraying on coffee plantations

The choice of spray tip and its working characteristics are some of the main factors that influence the loss of phytosanitary products. Choosing and making appropriate use of tips are fundamental factors for improving precision and safety conditions in the application.

Knowledge of working conditions and, mainly, the performance of equipment spraying phytosanitary products is a basic element for an adequate and efficient application, guaranteeing biological effectiveness and environmental safety at the same time.

The type of spray tip and its working characteristics are some of the main factors that influence the loss of phytosanitary products. Therefore, the choice and appropriate use of these tips constitute important steps towards improving precision and safety conditions in the application.

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Empty conical jet nozzles are traditionally recommended for applications in crops with a large leaf mass, where penetration and coverage are essential. Because they normally work at higher pressures than other types of tips, they produce very small droplets, sometimes smaller than 100 microns (µm). However, many researchers report that this droplet size class suffers more intensely from weather phenomena, presenting a high risk of drift.

As a result, there is a variant of this tip on the market, with air induction, which produces larger diameter droplets, minimizing losses due to drift. Droplets with a diameter greater than 500µm have little problem with drift. A disadvantage of these drops is that, due to their weight, they usually have greater difficulty attaching themselves to the leaves, running down to the ground. However, some producers envisage the possibility of replacing empty conical jet nozzles with others that are more environmentally safe, as long as application efficiency is not compromised.

In this sense, this work aimed to determine the drift generated by empty conical jet spray tips with and without air induction in applications in coffee cultivation.

Field applications

The field activities were carried out in the Coffee Production Sector of the Federal University of Uberlândia, in the city of Uberlândia (MG), with the help of Fapemig and CNPq.

In the applications, a hydropneumatic sprayer (Montana, Arbo 360) was used. It is a mounted sprayer, equipped with 12 nozzles, six on each side of the arch, coupled to a 4 x 2 tractor with a 65 hp engine (Massey Ferguson, 265E).

Two types of spray tips were used: empty conical jet ATR 80º Orange 3,0 and empty conical jet with air induction TVI 8002.

In all applications, a spray volume of 400L/ha was used. The average working speed of the group was 8,2km/h. The tractor engine speed adopted during operation was 1.800rpm to obtain 540rpm at the power take-off. The working pressures of the ATR and TVI spray tips were 1,567MPa (227,5Lb/in²) and 1,447MPa (210Lb/in²), respectively, and according to the manufacturer, at these pressures these tips produce very fine and very thick drops.

The tracer added to the syrup for subsequent quantification was rhodamine B (Synth, Diadema, Brazil). A concentration of 100mg/L was used.

The applications were made on a coffee plot of the red catuaí variety, spaced 3,8m between rows and 0,7m between plants, three years old, with an average height of 2,5m. The average lower diameter of the canopy was 1,2m.

Spraying was always done in pairs, conducted in a randomized block design in a split-plot scheme in a 2x20 space with ten replications, the first factor being referring to the spray tips and the second, the number of distances in relation to the last sprayed line.

Drift assessment

Prior to applications, polyethylene plates with dimensions of 0,40m x 0,08m x 0,006m were placed close to the ground in an area adjacent to the crop outside the treated area, in the direction of the wind, from a distance of 2,5m from the center of the crop. last spray pass up to 50m, spaced 2,5m apart, totaling 20 distances in relation to the last line sprayed. This same arrangement was repeated in four rows, spaced 1,5 m apart in the same direction of travel of the sprayer. The last four rows of plants were sprayed, for a length of 50m.

Filter papers with neutral pH and weight of 65g/m were fixed on the polyethylene plates.² with dimensions of 0,38m x 0,07m.

To carry out the applications, the methodology described in the ISO 22866 standard was followed.

Tracer quantification

At the end of the field part, rhodamine B was extracted and quantified from the papers. With data on the concentration of rhodamine B extracted from the papers, knowing the volume of syrup and the actual concentration of the syrup, the deposit of the tracer per unit area of ​​the drift collectors was determined, expressed in microliters per square centimeter (μL /cm²).

Results

Applications made to the coffee tree with the empty conical jet nozzle with air induction (TVI) caused less drift than the empty conical jet nozzle without air induction (ATR) up to 20 meters away from the last sprayed line. From this distance, there was no difference between the two ends. In this way, the air induction tip reduced the drift of the spray to the areas closest to the crop, as these tips produce drops with a larger diameter than the volumetric median, resulting in drops of greater mass, which makes it difficult to be dragged by the wind.

In some cases, increased drift may occur with air induction nozzles at distances closer to the treated area, due to the passage of thick drops through the lower part of the plants. However, in this experiment the crown of the plants was close to the soil surface, preventing this from happening.

Therefore, the TVI nozzle can be a good option for spraying in which the coffee plantation is located close to regions where drift should be reduced as much as possible, such as neighboring crops sensitive to the applied product, watercourses and habitable areas. However, when recommending it, the deposition of grout must be taken into account. Silva et al (2013) observed that, at a volume of 500L/ha, empty conical jet nozzles with and without air induction resulted in similar deposition of syrup in the lower and upper thirds of coffee trees.

Regarding control efficiency, Fießleden (2004) observed no significant differences in the control of different pests using conical jet nozzles with and without air induction. This same author stated that although the results are promising for air induction tips, studies are needed to more precisely define the effect of applications when systemic products are not used to control very small targets.

The highest percentages of drift were obtained at the collection point closest to the culture, decreasing as it moved away from the treated area. Above 20m, the drift percentage was below 1%. However, at no distance was this value null, even at 50m using the air induction tip.

The closing thought

Air induction empty conical jet nozzles reduced drift up to 20m away from the treated area. From this distance, tips with and without air induction generated the same drift. In this sense, the appropriate selection of spray tips is a good strategy for the farmer to reduce drift problems in foliar applications on coffee plants, making them more environmentally safe.

Guilherme Sousa Alves, João Paulo Rodrigues da Cunha, Federal University of Uberlândia

Article published in issue 169 of Cultivar Máquinas