Effects of ambient wind on droplet deposition uniformity in orchard air-assisted sprayers

Abstract To investigate the influence of the ambient wind on pesticide droplet deposition and drift loss patterns inside and outside the canopy of fruit trees, spraying tests were carried out under different ambient wind conditions. The results showed that due to the shielding effect of branches and leaves, droplets mainly concentrated in the middle and lower part of the canopy, and the coverage rate of droplets in the middle and lower canopy was 27.14% and 39.46% at a wind speed of 0.47 m/s. The droplet coverage rate decreased to 17.88% in the upper canopy, and the coefficient variation increased to 118.65. In addition, upwind spraying increased ground deposition of droplets in the downwind of 0–4 m and the airborne drift of droplets at a height of 3–4.5 m. Still, it decreases the deposition distance of droplets in the downwind. Compared with the direction of tractor moving against the wind, downwind driving reducing the penetration of droplets in the canopy, the loss of droplets in the air and the ground deposition in the downwind. The research and findings presented in this study provide critical insights for predicting droplet drift and ground deposition under varying wind conditions, optimizing field operational parameters, improving canopy distribution uniformity, and enhancing pesticide utilization efficiency.