Droplet Size Spectra And Drift Effect Of Two Phenmedipham Formulations And Four Adjuvants Mixtures

Relative drift potential was evaluated for three types of hydraulic nozzles (a flat-fan nozzle, a hollow cone nozzle and an air induction nozzle) spraying different liquids: water, emulsifiable concentrate (EC) and suspension concentrate (SC) formulations of phenmedipham dispersed in water, with or without addition of 4 different tank-mix adjuvants. The droplet size spectra were measured for these 15 spray mixtures using a Malvern Particle Sizer and characterised by the Volume Median Diameter (VMD) and the percentage of liquid contained in droplets less than 100 m (% < 100 m). Horizontal ground drift was measured in a wind tunnel, on glass fibre collectors using a fluorescent tracer dye technique. The relative drift of each spray mixture was characterised by the Drifted Part (DP) which is the part of the sprayed volume drifted between 2 and 6 metres. Although the nozzle type was the predominating parameter regarding to the droplet size spectra and the DP, differences were observed due to the liquids characteristics. The EC formulation produced a smaller droplet size and a greater DP than the SC formulation whatever the tank mix adjuvant used. For the different spray mixtures, the DP was poorly correlated to the VMD or the % < 100 m. However, correlations between the VMD, the % < 100 m and the DP of the flat-fan nozzle and of the hollow cone nozzle were significant. This suggests that a reference nozzle could be used to estimate the drift potential of other nozzle with a similar liquid sheet break-up mechanism.