Plant spraying quality when used by drone-robots

The study aimed to evaluate how airflow from a small drone’s rotor affects the accuracy and consistency of liquid coverage on individual plants or small plant groups during low-altitude spraying. The research focused on the future possibility of using drones - unmanned aerial vehicles (UAVs) as autonomous robots for plant protection. The effects of UAV propellers’ rotation on changes in droplet stream, produced from a single spray flat fan nozzle, as well as the influence of altitude, flight speed, and leaf area index (LAI), on the liquid coverage uniformity (CU) of application on plants were examined. The rotational speeds of the UAV propellers were set at 0.0, 5000, and 6400 rpm. Rapeseed and potato plants were selected for testing because they are common food crops and sources of raw materials for biofuel production. The UAV, on a laboratory test stand, was moved at two heights (H = 0.5 and 1.0 m) at two speeds (v = 0.54 and 1.0 m·s-1). The airflow from the UAV’s rotors narrowed the droplet stream produced by the nozzle by about 20% and increased the liquid volume in the center of the droplet stream, especially at a UAV height of H = 1.0 m. The leaf area index (LAI) for rapeseed was 0.877, and for potatoes it was 6.273. These LAI differences resulted in the liquid sprayed from the UAV settling more evenly on rapeseed plants than on potato plants. UAV flight altitude and leaf area index (LAI) appeared to be key factors affecting the amount of liquid applied to plants. Lower altitudes (H = 0.5 m) improved liquid application uniformity and enabled deeper penetration into dense foliage. High LAI values significantly hampered liquid penetration into lower plant levels and reduced the uniformity of liquid application.