The OML-SprayDrift model for predicting pesticide drift and deposition from ground boom sprayers

In order to predict the exposure of hedgerows and other neighboring biotopes to pesticides from field-spray applications, an existing Gaussian atmospheric dispersion and deposition model was developed to model the changes in droplet size due to evaporation affecting the deposition velocity. The Gaussian tilting plume principle was applied inside the stayed track. The model was developed on one set of field experiments using a flat-fan nozzle and validated against another set of field experiments using an air-induction nozzle. The vertical spray-drift profile was measured using hair curlers at increasing distances. The vertical concentration profile downwind has a maximum just above the ground in our observations and calculations. The model accounts for the meteorological conditions, droplet ejection velocity and size spectrum. Model validation led to an R2 value of 0.78, and 91% of the calculated drift values were within a factor of four of the measurements. © Pesticide Science Society of Japan