Insights on droplet drift and effective utilization of pesticide in “Third Pole”：Qinghai-Tibet Plateau of China

Crop protection pesticide spraying aims to greatly improve the utilization rate of pesticides. Controlling pesticides deposition requires a thorough understanding of the spatial behaviour of spray droplets.The Qinghai-Tibet Plateau, which is the headwaters of three largest water resources (Yangtze, Yellow and Lancang) in China, has exceptionally unique climatic characteristics. The goal is to reduce the amount of pesticides entering water resources. The wind tunnel experiment was used to validate the discrete phase method for tracking the trajectories. Cooperation between the smaller and larger droplets (greater than 150 μm) in the dense area around the nozzle can undoubtedly enhance the initial dispersion of droplet sizes. Droplet coalescence, which lowers the proportion of readily dispersed droplets, can greatly boost droplet deposition onto the target location.The crucial drift height is presented and clarified when droplets gradually disperse by identifying the descending length at which efficiency of mass transit starts towards decrease off quickly. The pesticide transport efficiency will not be enhanced by reducing the initial relative spread of droplets if the actual spray height surpasses the crucial drift height, and may even worsen drift loss. The temperature and relative humidity of the air have a greater influence on the evaporation losses of droplets smaller than 150 μm. In addition to providing information about pesticide spraying, the results of studies on droplet drift behaviors also suggest a method for controlling drift.