Evaluation of DJI AGRAS T30, Airplane, and Ground Sprayer Spray Deposition on Tassel-Stage Corn

Mid- to late-season crop protection in tall crops like corn often relies on aerial spraying, including with unmanned aerial vehicles (UAVs). However, information on UAV spray consistency remains limited. This study compared spray depositions from a DJI Agras T30 UAV, airplane, and ground sprayer on tassel-stage corn to simulate fungicide applications, while assessing the influences of key UAV operational parameters and the use of drift reducing agent (DRA). At the Alabama site, UAV applications without DRA increased spray dye concentration by 145.8% on upper leaves and 51.1% on ear leaves compared with airplane applications at 18.7 L ha−1. DRA 1 reduced upper leaf deposition, but both DRAs improved ear leaf deposition relative to no DRA and airplane treatments. UAVs without DRA and airplanes showed similar variability in dye concentration, while DRA use enhanced deposition uniformity. At the Georgia site, no treatment differences were found on ear leaves, but UAV and ground sprayer treatments produced higher upper leaf deposits than airplane application. Increasing UAV swath by 1.5 m at 2.4 m height reduced deposition, while a 4.6 m swath increased it, regardless of altitude. Overall, results suggest that downwash from UAV propellers enhances spray deposition within the crop canopy, and DRAs further improve this effect and influence spray uniformity. Additional studies on UAV spray parameters and droplet size are needed to better understand downdraft influence.