Pesticide deposition rates and droplet parameters of different plant protection instruments applied at different growth stages of rice

The evaluation of the pesticide spraying efficiency of different plant protection equipments could provide theoretical and technical support for pesticide reduction and pest control on rice. The method used in this study was referred to an agricultural industry standard the determination method of pesticide deposition rate (NY/T 2677—2015). Experiments were carried out in the late rice field of direct seeding in Quanan town, Nanxiong City, Guangdong Province. The pesticide utilization rates and droplet parameters of manual sprayer, electric sprayer, and plant protection unmanned aerial vehicle (UAV) were analyzed. The results were as follows. There were significant differences in pesticide deposition rates of different sprayers at the same rice growth period which showed as UAV>electric sprayer>manual sprayer. The average pesticide deposition rates of manual sprayer, electric sprayer, and UAV were 18.33%, 24.58%, and 35.84% respectively at the seedling stage, 24.72%, 35.28%, and 45.15% respectively at the closure stage, and 32.39%, 40.29%, and 52.42% respectively at the rupturing stage. On the other hand, there were significant differences in pesticide deposition rates of different stages of rice with the same sprayer, which was the rupturing stage>the closure stage>the seedling stage. The results of deposition distributions showed that the deposition values of different rice layers of UAV treatments decreased from top to bottom, and the droplet deposition was mainly concentrated on the upper and middle rice layers by using manual and electric sprayers. In addition, thedroplet size results showed that the size of droplet sprayed by UAV was significantly smaller than that of manual and electric sprayer, and also better with the uniformity. Droplet density results indicated that the dispersion of UAV droplets was better than manual and electric sprayers. Compared with the traditional sprayers, the UAV greatly improved the pesticide deposition rate and the atomization effect of pesticide solution.