Performance of variable-rate airblast sprayer retrofitted with stereo vision controlled spray system for vineyard applications

Optimizing spray application efficiency in 3D crops remains a major challenge due to the spatial and temporal variability of canopy structure. Variable-rate spray (VRS) technologies have emerged as a promising solution to address this limitation by adapting spray output to canopy characteristics. Stereo vision systems have recently gained attention as a cost-effective real-time canopy detection sensor. Despite encouraging results, previous research has been conducted with prototype sprayers. In this study, a commercial airblast sprayer retrofitted with a stereo vision controlled spray system was evaluated and compared with a constant-rate spray (CRS) application across three grapevine growth stages (BBCH 53, 57, and 77). Spray volume, canopy deposit, spray coverage, airborne drift, and ground drift were assessed. The VRS application reduced spray volume by 79.6% and 43.0% at the early and middle growth stages, respectively, whereas a 22.0% increase was observed at the late growth stage compared with CRS application. Despite the spray volume reduction at the early growth stage, canopy deposit and spray coverage decreased to a lesser extent. At the middle and late growth stages, canopy deposit and spray coverage were higher with VRS application than with CRS application. Airborne and ground drift were reduced by 29.3% and 48.9%, respectively, at the early growth stage. At the middle growth stage, airborne drift increased by 44.0% while ground drift decreased by 23.0%. At the late growth stage, airborne and ground drift increased by 30.9% and 55.9%, respectively. Despite promising results, further optimization of spray dose according to canopy development is required.