Effect of spraying drone flight parameters on vineyard canopy coverage and droplet deposition

Unmanned Aerial Vehicles (UAVs) are increasingly promoted as alternatives to conventional plant protection product (PPP) spraying in vineyards, yet limited evidence exists on how flight parameters and application configurations influence spray deposition under real vineyard conditions, especially within Europe. This study evaluated the performance of a DJI Agras T16 spraying drone across eight operational configurations combining two flight altitudes (2.0 and 2.5 m AGL), two flight speeds (1.0 and 1.5 m/s), and two aircraft positioning strategies (over-row and inter-row). Spray deposition, canopy coverage, and ground losses were quantified using water-sensitive papers (WSPs) positioned at multiple canopy heights and ground locations, while meteorological conditions were monitored, following methodologies adapted from the ISO 22,866/22,522 protocols. Results showed strong interactions among altitude, speed, flight path, and wind parameters, with over-row treatments concentrating deposition in upper canopy layers and inter-row treatments producing more homogeneous profiles but higher sensitivity to wind direction. Lower altitude flights (2.0 m) combined with slower speed (1 m/s) substantially increased ground deposition regardless of UAV positioning, whereas higher altitude (2.5 m) and speed values (1.5 m/s) reduced spray losses to the ground. The increase in pump output associated with higher speed under a constant application rate is expected to produce finer droplets, which can enhance penetration but may also elevate in-field drift risk. These findings demonstrate that UAV spraying performance depends on integrated optimisation of operational settings and environmental conditions. The results provide practical guidance for improving drone-based vineyard spraying and highlight the need for updated EU regulatory frameworks tailored to UAV application characteristics.