Adjuvantes e taxas de aplicação na pulverização de fungicida na cultura da soja

Abstract

The application technology of plant protection products, when well used in the field, provides an adequate transport of the biologically active product to the target, avoiding losses and increasing the effectiveness of the treatments. The objective of the present work was to evaluate the effect of different application rates associated with different adjuvants on the application of fungicide in the soybean crop, as well as the interactions between adjuvants and the fungicide azoxystrobin + benzovindiflupir on the physicochemical characteristics, droplet evaporation, leaf spread and spectrum of drops of the spray mixture. In the first field study, it was evaluated the deposition of the spray solution in soybean plants and the physicochemical characteristics of the spray solution. The experiment was carried out in a randomized block design, with 4 replications, in a 2 x 2 x 2 factorial scheme, being two volumes of spray solution, addition of mineral oil based on aliphatic hydrocarbons (presence or absence) and addition of vegetable oil based on orange essential oil (presence or absence). In the second study conducted in the laboratory, physical-chemical characteristics, evaporation and droplet spectra were evaluated. For the evaluation of the spectra of drops (diameter of volumetric median, relative amplitude and percentage of droplet volume less than 100 μm), evaporation and physical-chemical properties (pH, electrical conductivity, viscosity and surface tension), the experiment was performed in a 2 x 6 factorial scheme, the first factor being the absence or presence of the fungicide and the second factor the different sprays solutions (five adjuvants and water). The leaf spreading evaluation was performed in a factorial scheme 6 x 2 x 3: six spray solutions submitted to the presence or absence of the fungicide, on three foliar surfaces (corn, soybeans and cotton). It was possible to observe that the increase of the rate of application and the use of mineral oil provide higher deposits in the upper and middle thirds and in the upper third of the plants, respectively. In both studies, there were changes in the physicochemical properties inherent to the spray solution, being influenced by the combination between adjuvants, rate of application and fungicide. All adjuvants improved the spray quality on the characteristics of the droplet spectrum by reducing droplets smaller than 100 μm and standardizing the spectrum. The adjuvants increased the leaf spreading of the droplets, but this characteristic was influenced by the leaf morphology of the target culture.