Effect of different spray factors on weed control in wheat field by unmanned aerial vehicle

In order to clarify the effects of different spray factors, such as spray volume, droplets size and spray adjuvants, on Jifei P20 UAV for thecontrol of weeds in wheat fields, the experimentswerecarried out using mesosulfuron-methyl 30 g/L SC +paradigm arylex 20% WDG as a model herbicide in 2019. The results of deposition experiment showed that the worst deposition (0.67 μg/cm²) was observed by the treatment of low spray volume (11.25 L/hm²) and the corresponding deposition rate was only 22.37%. The treatment of large droplet size with 1.07 μg/cm² deposition and the deposition rate 35.62% was slightly lower than that of other treatments using UAV (deposition was 1.16-1.52 μg/cm² and the deposition rate 38.73%-50.83%), but significantly lower than conventional spray with deposition rate 67.00%. The results of weed control experiment showed that the optimum spray volume was 15.0-22.5 L/hm². And the total fresh weights of weeds were 74.8%, 85.9% and 88.2% by using the spray volumes of 11.25, 15.0 and 22.5 L/hm², respectively.The optimum sprinkler head was the medium-size one. The total weed control efficiencies using small, medium and large droplet sizes were74.8%, 85.9% and 88.2%, respectively. The optimum spray adjuvants were EDDF and Maifei, and their control effects on the total fresh weights of weeds were 88.9% and 87.4%, respectively. The deposition using the conventional spray was 2.01 μg/cm², and the fresh weight effect was 87.6%. The Jifei P20 UAV has the advantage of time- and water-saving under suitable spray factors. Although the droplet deposition was lower than that of conventional spray, but the weed control effect was not much different from that of conventional spray. .