Management measures for the mitigation of spray drift of very fine droplets sprayed by a spraying robot

Pesticide spraying is one of the most significant processes in agricultural production and one of the most complicated, risky agricultural operations. Side effects of pesticides can cause acute poisoning and serious chronic diseases in humans. Robotic spraying in agriculture is one solution to avoid human intervention. However, there has been little research on the distribution of droplets and unwanted spray drift when spraying with ground spraying robots equipped with jet spraying systems. This study analyses the downwind spray drift of three drift reduction agents (DRAs) depending on the lateral wind velocity using a ground spraying robot equipped with a jet spraying system in the field under conditionally controlled conditions. The three DRAs investigated were: DRA1 (100% anionic polymer dispersion), DRA2 (calcium dodecylbenzene sulfonate 50%, butanol 18%), and DRA3 (C10-13-alkyl derivatives, calcium salt 37%, butanol 15%). DRA solutions at a concentration of 0.1% (water as control) were sprayed with a jet spraying system and analyzed at four different droplet diameter levels ranging from VMD_preset=60 μm to 120 μm, with a change every 20 μm. The study showed that the atomization level of droplets had a significant effect on the impact of spray drift: the smaller the droplets are sprayed (VMD_preset=60-80 μm), the lower the effectiveness of DRA (spray drift can be reduced by about 2.5-fold) while spraying larger droplets (VMD_preset=100-120 μm) with DRA reduces drift by about 3.5-fold (at the lateral wind of 4 m s^-1). The use of DRAs also significantly impacted the reduction of spray drift. All DRA solutions were significantly more effective at low lateral winds (2-4 m s^-1). Moreover, the difference between the effectiveness of DRA solutions decreases with increasing lateral wind velocity from 2 to 10 m s^-1. In summary, the following management measures can be used to control droplet drift using a robotic jet spraying system, in order of importance: lateral wind velocity, selection of the level of droplet atomization, and the use of DRAs. This can help to find the optimal solution to ensure optimal coverage of plants with plant protection products and to minimize losses and negative environmental impacts.