Intelligent sprayer enhances drift reduction: Wind condition correlation and comparative field study in ash tree applications

Spray drift from pesticide applications poses serious risks to the environment, human health, and neighboring crops. This research evaluated and analyzed off-target spray drift reduction potentials of an axial-fan air-blast sprayer retrofitted with a laser-guided variable-rate application (VRA) technology by comparing with a conventional constant rate application (CRA) in a nursery ash tree field under variable wind conditions. Airborne and ground level drift were measured at multiple downwind distances and sampling heights. Meteorological parameters were continuously recorded. Deposition, ground coverage, and droplet deposit size characteristics were measured through fluorimetry and image-based analysis. Drift behavior was examined within two zones: the Protected No-Spray (PNS) Zone (5 m downwind) and the Downwind Drift Transport (DDT) Zone (5 and 105 meters downwind). VRA reduced spray volume by up to 51.2% while maintaining effective canopy coverage. In the PNS Zone, airborne drift was reduced by 64.4% to 79.5% across three lateral sampling locations. In the DDT Zone, VRA achieved reductions of 66.7% at 5 m, 58.3% at 15 m and 50.0% at 35 m with drift undetectable beyond 35 m. At the ground level, VRA resulted narrower and lower range of droplet deposit density with volume median diameter (VMD) consistently below 1000 µm. Regression analysis addressed that CRA drift was strongly influenced by wind conditions (R² > 0.65), whereas VRA showed weaker correlations (R² < 0.35), reflecting better drift control stability. These results demonstrated that VRA effectively mitigated off-target drift, improved spray uniformity, and provided improved drift control under varying wind conditions.