Evaluation of Droplet Deposition Distribution in Apple Orchards Using a Ground-Air Combined Unmanned Spraying Model

To address the challenges of low mechanization and uneven canopy coverage in traditional orchard spraying, this study proposes a ground-air combined spraying technique. This approach integrates a plant protection drone and vehicle into a coordinated model to ensure comprehensive orchard coverage. The drone employs three-dimensional route planning, while the vehicle utilizes automatic route planning via a smart cloud platform. Field experiments were conducted to examine droplet deposition patterns and to optimize operational parameters. Results indicated a gradual reduction in droplet deposition from the upper to lower canopy layers during drone spraying. Increasing the drone’s spray volume notably improved spray distribution, particularly in the upper and middle canopy layers, achieving an average twofold increase. Furthermore, the SX110015VS nozzle demonstrated superior droplet deposition, while the SX11001VS nozzle provided broader spray coverage. For vehicles, droplet deposition and coverage decreased progressively from the lower to upper canopy layers. In the ground-air combined spraying tests, the unmanned coordination of drone inter-row flight mode with the plant protection vehicle resulted in more uniform coverage and better penetration across canopy layers, achieving nearly complete and even coverage. Compared to using drones or vehicles alone, the combined model significantly enhanced droplet deposition and spray distribution, particularly on both sides of leaves. Additionally, coverage uniformity and droplet penetration were improved, with reduced variation. This study provides critical data support for developing optimal operational standards for unmanned ground-air combined spraying, offering practical guidance for achieving uniform droplet coverage in modern orchards.