The droplet and atmospheric dispersion drift (DAD-drift) model - A modular approach for estimating spray drift at the...

Spray drift describes the off-target movement of pesticides by wind during or immediately after application, and its mechanism is highly complex and influenced by many factors. Spray drift modeling has become an increasingly important tool as spray drift field experiments are very expensive to conduct. Many modeling approaches are available to describe spray drift deposition after aerial and ground application at the field scale. We have developed a novel modeling approach to predict spray drift deposition after ground application at the landscape scale. The Droplet and Atmospheric Dispersion drift (DAD-drift) model combines a mechanistic droplet model, a micrometeorological model, and a three-dimensional Gaussian diffusion model. It is an iteration of the two-dimensional tilting plume approach and allows for the prediction of spray drift deposition from ground spray applications while accounting for environmental conditions, spray nozzle characteristics, and spray application characteristics. The DAD-drift model was evaluated against two field trial studies for a wide range of environmental conditions (i.e., temperature, humidity, wind speed) and four spray nozzles (fine to ultra-coarse). Model predictions were in very good agreement (R² = 0.931, RSR = 0.260) with spray drift observations from these studies, demonstrating the applicability of the model over a wide range of conditions. During a one-at-a-time sensitivity analysis, the model showed clear and understandable behavior when input parameters were varied. Droplet size distribution, boom height, temperature, wind speed, and atmospheric turbulence were identified as the most important factors.