Deposition of spray applied to a soybean crop using an unmanned aerial vehicle

Abstract

The use of unmanned aerial vehicles (UAVs), or drones, to apply crop protection products has been increasing; however, because this is a recently developed technology, data about its efficacy in many crops are still scarce. The objective of this study was to evaluate the deposition of a spray applied to a soybean crop with a UAV at two flight speeds and compare it to that of spray applied with a ground-based sprayer. The experiment used a DJI AGRAS MG-1 UAV to spray a soybean crop at the R3 growth stage. The experiment consisted of three treatments with eight replicates for each; the spray was applied using the UAV flying at 15.4 km/h or 21.8 km/h or a CO 2 -pressurized backpack sprayer. The application rate was 10 L/hm 2 with the UAV and 115 L/hm 2 with the ground-based sprayer. The following parameters were evaluated: deposition of a tracer added to the spray solution (500 g/hm 2 in all treatments) in the upper and middle parts of the soybean plants using spectrophotometry and droplet coverage, density, and size spectrum using water-sensitive paper cards. Flight speed did not alter droplet coverage, density, or spectrum. The coverage in the middle layer of the soybean canopy was low whether application was by the ground-based application (1.2%) or by the UAV (0.2%), which demonstrated the difficulty of reaching that part of the plants. Tracer deposition in the upper and middle parts of the soybean plants from the UAV was similar to that obtained with the ground-based application.