Direct and indirect drift assessment means, Part 3: Field drift experiments

A whole series of field drift experiments were performed to investigate the effect of nozzle type (flat fan, low-drift, air inclusion) and size (ISO 02, 03, 04 and 06) on sedimenting spray drift. Sedimenting spray drift was determined by sampling in a downwind area at 24 different positions using horizontal drift collectors in combination with a fluorescent tracer with measurements up to 20 m from the directly sprayed zone. Meteorological conditions were continuously monitored. Based on 27 drift experiments with the reference spraying at various environmental conditions, the important effect of atmospheric conditions on the amount of near-field sedimenting spray drift was demonstrated and quantified. A non-linear drift prediction equation was set up and validated. This equation was used to compare the drift results of the different spraying techniques under various weather conditions with the reference spraying by calculating their total drift reduction potential (DRP_t). Air inclusion nozzles have the highest drift reduction potential followed by the low-drift nozzles and the standard flat fan nozzles and the effect on drift deposits is high with DRP_t values varying from -136.5 up to 89.8%. The effect of nozzle type is most important for smaller nozzle sizes A large database with (absolute) near-field drift results is made available to enlarge the international drift database with information about the effect of climatological conditions and spray application technology. The results are generally in good agreement with the results from different other studies although drift studies are difficult to compare due to differences in weather conditions, spray application techniques, methodologies and crop conditions.