Spray deposition from an unmanned aerial vehicle on a coffee crop

Abstract

The use of unmanned aerial vehicles (UAVs) to apply pesticides has grown significantly, but technical data to support improvements in application efficiency are lacking, especially for perennial crops. This study aimed to determine the best operational parameters for the application of pesticides to coffee plants using UAVs. The experiment consisted of 8 treatments and 4 replicates in a 2x2x2 factorial design: two spray mixture compositions (solutions with spreading adjuvant and mineral oil), two spray nozzles (XR flat-fan nozzle and Airmix flat-fan nozzle with air induction) and two spray volumes (10 and 20 L ha-1). Spray solution deposition was evaluated by spectrophotometric detection of a tracer in leaves from the upper and lower parts of the coffee canopy, and spray coverage, droplet density and droplet size were evaluated using water-sensitive paper. The surface tension, pH and electrical conductivity of the solutions were also evaluated. The air induction nozzle was more suitable than the standard nozzle for UAV application, as the former yielded greater deposition of spray solution. Mineral oil improved the spray deposition on the coffee leaves, although the spreader reduced the surface tension to a greater extent. The higher spray volume increased the droplet density, as well as the coverage, which is very relevant, especially whit contact pesticides.