Landscape-level assessment of spray drift – A virtual experiment using the Droplet and Atmospheric Dispersion drift (DAD-drift) model

Spray drift significantly contributes to the off-target movement of pesticides. While factors influencing spray drift at the field scale, such as environmental conditions, equipment, and buffer zones, are well understood, deposition at landscape scale, is influenced by additional factors including landscape characteristics and the proximity of non-target areas. The DAD-drift model accounts for the physical basis of spray drift, application location, wind direction, and deposition at the landscape scale. In a virtual experiment we compared DAD-drift with simplified spatial representations of application areas, commonly used in other modelling approaches, the results showed large differences in spray drift predictions. In a second virtual experiment, results from DAD-drift were analyzed using multiple linear regressions to identify spray drift drivers at the landscape scale. Results showed that the droplet size distribution, determined by nozzle type, closely followed by proximity to non-target area, are the two most influential factors determining deposition in non-target areas. • Off-target spray drift is highly complex at the landscape scale. • Spatiotemporal variation of conditions and landscape organization are drift drivers. • Simplified spatial representations lead to uncertain spray drift predictions. • Droplet size distribution and distance are most relevant drivers at landscape scale. • Effect directions of wind speed, temperature and humidity are distance dependent.