Modelling pesticide dispersal over a vineyard canopy during spray application

Pesticide drift is a major pathway of atmospheric pollution during spray application. As vineyards usually require a large number of spray applications per year, they represent a major potential factor of air pollution in agricultural areas. Assessing pesticide loss to the atmosphere from a vineyard canopy requires a good knowledge of mass and momentum exchange processes between the canopy and the atmosphere. For this purpose a Large-Eddy Simulation (LES) airflow model has been coupled with a Lagrangian droplet dispersal model. In parallel, pesticide droplet fluxes as well as turbulent wind flow have been measured over an artificial vineyard during spray application from a tractor.

The model is solved within an atmospheric domain that includes the whole experimental plot. The main characteristics of the simulated turbulent wind flow over the vine rows are first presented. It is shown that they differ following the angle between the wind direction and the vine row direction. Droplet dispersal in the atmosphere and deposition on the ground are then simulated in several atmospheric conditions and compared to the measurements. Finally, the impact of the spray application system itself (tractor and sprayer) on wind flow and droplet emission is discussed.