Research was carried out concerning spraying young cherry trees with a multirotor drone: a hexacopter. The aim of the study was to evaluate the impact of the following: the nozzle type, the air stream from the drone rotors and the size of spacing between the trees on the distribution of the liquid sprayed in the crown of the trees being sprayed. Experimental trials were conducted on a laboratory test stand. Air-injector spray nozzles: single and a twin flat were used interchangeably to spray the liquid. The travelling speed of the drone was 1.0 m∙s⁻¹. A drone of 106.7 N weight was accepted in the study. The value of the spray liquid deposited and the uniformity of the liquid deposition in the crowns of the trees as well as the transverse distribution of the liquid under the nozzles were evaluated. It was found that the air stream from the drone rotors increased the distribution of the liquid on the trees sprayed, mainly at the middle and lower levels of the crown. A higher deposition value of the liquid was sprayed from the twin flat nozzle than from the single flat nozzle. There was no significant effect of the difference in the distance between the trees, of 0.5 and 1.0 m, on the liquid distribution. Under the influence of the air jet, the uniformity of the liquid distribution in the crowns of the trees also improved.

The study aimed to assess the quality of spraying of ornamental conifer using a multi-rotor drone. We examined how the speed of drone movement and the propellers’ spin speed can affect the deposition quality of the sprayed liquid in the crown of blue spruce (Picea pungens Engelm.). Due to the avoidance in the future of droplet drift by air movements, an air injector atomiser for liquid spraying was used, and a low altitude of 0.6 m of the drone flying above the tree was used in the study. The drone moved at two speeds: 0.57 m·s^–1 and 0.94 m·s^–1. The propellers’ spin speeds were adjusted based on the drone’s weight with the spray liquid tank filled and empty. The propellers’ zero-spin rate was also included to compare the drone to a field sprayer. The tests were conducted in a laboratory setting. Volume and uniformity of liquid volume settled on the levels of samplers positioned on a tripod within the tree canopy were assessed. The samplers were placed in two zones of the tree: near the tree trunk and at a distance of 0.21 m from the trunk. Airstream speed generated by drone propellers was also evaluated inside the tree. The findings indicated that the rotations of propellers and air speed significantly influenced the quality of liquid deposition on samplers located away from the trunk. The results also showed that using a drone instead of a field sprayer could benefit the quality of the spray application. The weight of the multi-rotor drone, determined by the spray liquid tank’s filling level, can significantly impact the quality of spray deposition in the tree. Based on the investigations, it can be recommended that low-altitude spraying drones be adopted for studies and future strategies in precision agriculture using autonomous inspection-spraying drones.

On a mounted laboratory stand, comparative tests were carried out on the effectiveness of spraying wheat plants with liquid using a multi-rotor drone. The study was undertaken with and without propeller rotations. The lack of rotations simulated spraying by a ground sprayer. The height of the drone’s displacement above the plants was similar to that of the nozzles above the plants used when spraying with field sprayers, 0.5 m and 1.0 m. The speed of the drone movement was 0.57 and 1.0 m·s⁻¹. The effects of the height and speed of the drone’s movement and the impact of the airflow on the volume and uniformity of the liquid application on the plants were assessed. In addition, changes in the transverse distribution of liquid volume in the droplet stream and the transverse distribution of the air velocity in its stream were evaluated. The liquid was sprayed at a constant pressure of 0.2 MPa. The study’s results show that the low height of the drone displacement not only had a strong effect on increasing the liquid volume applied to the plants but also improved the uniformity of application at plant levels. It was also noticed that, at a height of 0.5 m, there was a significant irregularity in the air stream under the drone.