Spray swath study in relation to canopy deposition during UAV spray applications in vineyards

Unmanned aerial vehicles (UAVs) have been raising interest for spray applications in 3D crops such as vineyards. When dealing with UAV broadcast spray applications, the preliminary study of the spray swath is a key factor. Indeed, an optimised fly path planned considering proper spray swath overlaps allows maximising the canopy spray deposition, avoiding under- or over-spray situations, and minimising off-target spray losses. This paper presents the correlation between the spray swath, filters upholstered on polystyrene cubes and the canopy deposition during UAV spray applications in a vineyard. Three arrays of Petri dishes (140 mm diameter) and iron poles (0.8 m height), used to host cubes of 50 mm edge that were upholstered by filter papers (90 g m−2 density), were set up outside the vine rows, while deposition in the canopy was measured using filter papers at three heights and depths per plant. Moreover, six configurations were tested based on the combination of different UAV flight modes (1way and 2way broadcast), nozzle type (conventional and air inclusion 110°, 03 and 015 size), and UAV cruise speeds (1 and 3 m s−1). Swath deposition and filters deposition on the cubes had a good correlation with the canopy deposition as the linear fitting curves had an R-square higher than 0.8. Also, the obtained spray swath allowed to optimise the UAV flight path planning, obtaining a distance between flight centerlines of 1.5 m.