Herbicide deposition and effective weed control achieved through optimized unmanned aerial vehicle flight height with DJI AGRAS T10

ABSTRACT The use of unmanned aerial vehicles (UAVs) in agricultural spraying is growing globally, but few studies exist on spray deposition of herbicides, such as glyphosate, and weed control efficacy in pre-sowing burndown. This study sought to evaluate the deposition of glyphosate, tracer, and the effectiveness of ryegrass control at different application heights with DJI Agras T10. Carried out in a winter fallow area with a predominantly ryegrass infestation, originating from natural sowing, the experiment was conducted in a completely randomized design, in a 4x7+1 factorial arrangement, evaluating flight heights of 3, 4, 5, and 6 m and, in the second factor, 7 evaluation points every 1m to measure spray deposition, with 5 replications and a total of 35 plots. The application mixture included glyphosate (1.25 kg ae ha−1), clethodim (0.12 kg ai ha−1), and the dye tracer Brilliant Blue (3g L−1). The deposited mixture was recovered and quantified through spectrophotometry. Increasing the flight height resulted in less application uniformity and lower glyphosate deposition, due to spray drift outside the experimental area, which impaired the effectiveness of burndown. However, application at 3 m provided greater deposition and uniform distribution along the strip evaluated. Tracer solution deposition was lower at heights of 3 and 4 m, with minimal variation at 7 m range. A height of 3 m was the best of the tested heights for burndown, ensuring uniform glyphosate and clethodim deposition and weed control of >90%.