Avaliação da qualidade de aplicação de fungicida na cultura da soja utilizando diferentes pontas de pulverização com diferentes taxas de aplicação

Abstract

The application of pesticides is one of the main ways to control the pathogens that plague the grain crops, and it is through the area of application technology that this fact is possible. Within this area, one of the main factors affecting the quality of the application is the spray tips, which are responsible for producing the characteristics of the sprayed droplets spectrum, and therefore greatly influence the final quality of the pesticide application. Some farmers opt for arbitrary application rates aiming high operational yields (hectares worked per hour) without considering the recommendation for the crop. For this, they calibrate the sprayer without considering the working pressure, going to the extreme that, in some cases, not even the pressure gauge is used in their machines. Such practices can result in problems in the quality of spraying and in order to verify the consequences of the problem described above, an experiment was conducted in the Precision Agriculture and Agricultural Mechanization Laboratory (LAPMEC) of the Federal University of Mato Grosso, Sinop Campus. Two commercially available spray tips were tested, using different application rates without considering the working pressure. An agricultural tractor with a 600 liter capacity sprayer was used for spraying, coupled to the three points. The experiment had 4 repetitions per treatment with evaluations made with hydrosensitive papers positioned in 3 parts of the plant (upper, middle and lower third), alternating between three flow rates: 50, 100 and 150 L ha-1 and the two types of tips of interest: empty cone type tip and 3D fan type tip. The collected data were statistically treated as a CBA (Randomized Block Design) in the subdivided plot scheme with a factorial design in the plot. The cone tip showed superior performance in the DMV and droplet density variables, but in relation to the application rate factor, the rate of 100 L ha-1 generated the best results about the DMV. The regions below the plant canopy were reached by droplets of smaller diameter, and these same regions have more difficulty to receive drops. Higher application rates improve the quality of coverage and droplet density. Under the conditions of the experiment, both spray tips did not reach the minimum values of DMV and density to be recommended for contact fungicides, that is, the inadequate use of working pressures results in a reduction in the quality of the spray tips.