Caracterização de gotas e risco potencial de deriva de aplicações de produtos fitossanitários

Abstract

The knowledge of the spectrum and drops speed is of paramount importance for a successful application of pesticides through a hydraulic spray, with good spray deposition on target and minimal damage to the environment. One of the most common technique for drift reduction has been the use of air induction nozzles, however, their behavior is not yet fully known due to the inclusion of air bubbles in its interior. Thus, the objective of this study was to evaluate the spectrum, the speed, the potential risk of drift and the amount of included air in drops generated by different spray nozzles with and without air induction, adding adjuvant to spray or not, on different operating conditions. Two experiments were conducted. The first experiment was conducted in a completely randomized design, with five replications, in a factorial 2 x 3 x 3 (two nozzles, three flow rates and three operating pressures). The second experiment was carried out in a completely randomized design, with five replications, in a factorial 2 x 2 (two spray nozzles and spray with and without mineral oil). The spectrum of the population of drops and the fall speed was determined directly, using a real time drops analyzer, which uses high resolution images for the analysis. The equipment VisiSize D30 (Oxford Lasers Imaging Division, England) was used in this study. The potential drift risk was evaluated by means of a wind tunnel. Spray nozzles with air induction by the manufacturers Teejet®, Hypro® and Magnojet® produced drops with a greater DMV than spray nozzles without air induction, and these increases ranged from 56.66; 63.31 to 128.61%, respectively. Pressure rise resulted in further reduction of the volumetric median diameter (DMV) as well as the relative amplitude and increase the average drops speed. The velocity of the drops presented little variation between the spray nozzles with and without air induction with the same pressure and flow rate, however, spray nozzles with larger flow rates produce drops with higher speeds. In general, the addition of mineral oil resulted in an increase in the drops velocity, reduced drift and a more homogeneous droplet spectrum. There is an inverse correlation between drift potential and the DMV of the drops generated, which indicates that it can be used to predict the behavior of potential drift.