Effect of Droplet Size Parameters on Droplet Deposition and Drift of Aerial Spraying by Using Plant Protection UAV

Abstract

In the field of pesticide spraying, droplet size is one of the most important factors affecting droplet deposition and drift. In order to study the effect of different droplet size parameters on droplet deposition distribution and drift of aerial spraying by using plant protection UAV, an aerial spraying test with the same spraying rate and different size droplets in rice canopy was carried out by using multi-rotor unmanned aerial vehicles (UAV) and four TEEJET nozzles with different orifice sizes (these droplets with a volume median diameter (VMD) of 95.21, 121.43, 147.28, and 185.09 μm, respectively), and the deposition distribution and penetration of droplets in the target area and the drift distribution of droplets in the non-target area were compared and analyzed. The results showed that the deposition distribution and penetration of droplets in the target area and the drift distribution of droplets in the non-target area were influenced by the droplet size. The droplet deposition rate in the upper and lower rice canopies were increased in the target area with the increase of droplet size. The penetration results of droplets also increased with the increase of droplet size, and that of droplets with a VMD of 185.09 μm was the best, reaching 38.13%. The average values of the cumulative drift rate of droplets in the rice canopy in the four tests were 73.87%, 50.26%, 35.91%, and 23.06%, respectively, and the cumulative drift rate and the drift distance of droplets decreased with the increase of droplet size, which indicated that the increase of droplet size can effectively reduce droplet drift. It demonstrated that the droplet size is one of the most important factors affecting droplet deposition and drift for pesticide spraying by plant protection UAV, and for the application of plant protection UAV with extra-low volume spraying, the use of droplets with VMD less than 160 μm should be avoided and a more than 10 m buffer zone should be considered downwind of the spraying field to avoid drug damage caused by pesticide drift. The results have fully revealed the effect of droplet size parameters on droplet deposition and drift of aerial spraying. Moreover, the influence of the wind field below the rotors on the distribution of droplet deposition was surmised and analyzed from the perspective of plant protection UAV. It is important for optimizing the droplet parameters of aerial spraying, increasing the spraying efficiency, and realizing precision agricultural aviation spray.

Performance evaluation of a multi-rotor unmanned agricultural aircraft system for chemical application

“…D V0.1 represents the volume of a small droplet (10% of the total deposited volume). D V0.5 and D V0.9 represent the volume of medium-sized and large droplets, respectively [46,47] .…”

Effects of droplet size and spray volume parameters on droplet deposition of wheat herbicide application by using UAV

“…This was different from our conclusion, which may be due to the different spray volume from our experiment. Chen et al [6] found that the percentage of spray coverage increased with the increase of the droplet size in the lower volume application. That was mainly caused by the drift of droplets.…”

“…It led to a low utilization rate and excessive spraying of pesticides and caused serious pesticide residues and environmental pollution [3][4][5] . According to reports, the use of pesticides in China was about 2.5 times the world average, and the arable area contaminated with pesticides accounted for about 1/10 of the arable area [6] .…”

Design of Variable Spray System for Plant Protection UAV Based on CFD Simulation and Regression Analysis

“…As shown in Figure 11 b, the nozzle flow is mainly reflected in the deposition volume rather than the ratio. However, the small droplet diameter is easy to be affected by wind, and the large droplet leads to nonuniform deposition, as shown in Figure 11 c. Therefore, finding a suitable droplet diameter is necessary [ 18 ]. The distance between the propeller and the nozzle is related to the distribution of downwash wind field.…”