UAV-spray application in vineyards: Flight modes and spray system adjustment effects on canopy deposit, coverage, and off-target losses.

Improvements in the spray application of plant protection products enhance agricultural sustainability by reducing environmental contamination, but by increasing food quality and human safety. Currently, Unmanned Aerial Vehicles (UAVs) are raising interest in spray applications in 3D crops. However, operational configurations of UAV-spray systems need further investigation to maximise the deposition in the canopy and minimise the off-target losses. Our experimental research focused on investigating the effects on the canopy spray deposition and coverage due to different UAV-spray system configurations. Twelve configurations were tested under field conditions in an experimental vineyard (cv. Barbera), derived from the combination of different UAV flight modes (band and broadcast spray applications), nozzle types (conventional and air inclusion), and UAV cruise speeds (1 and 3 m s-1). Also, the best treatment, among those tested, by using the UAV-spray system and a traditional airblast sprayer were compared. The data was analysed by testing the effects of the three operational parameters and their two- and three-way interactions by means of linear mixed models. The results indicated that the flight mode deeply affects spray application efficiency. Compared to the broadcast spray modes, the band spray mode was able to increase the average canopy deposition from 0.052 to 0.161 μL cm-2 (+ 309 %) and reduce the average ground losses from 0.544 to 0.246 μL cm-2 (- 54 %). The conventional airblast sprayer, operated at a low spray application rate, showed higher canopy coverage and lower ground losses in comparison to the best UAV-spray system configuration.