1. Assessment of a CDA rotary atomizer for weed control Ouled Taleb Salah S., Massinon M. and Lebeau F. Gembloux Agro-Bio Tech (University of Liege), Gembloux, Belgium ISOFAR / MOAN Symposium Sousse, Tunisia Assessment of a CDA rotary atomizer for weed control Ouled Taleb Salah S., Massinon M. and Lebeau F. Gembloux Agro-Bio Tech (University of Liege), Gembloux, Belgium ISOFAR / MOAN Symposium Sousse, Tunisia Introduction Crop protection is mainly achieved by spraying pesticides using hydraulic nozzles. This can lead to environmental contaminations that can be minimized especially in the context of reduction application rates. The challenge is therefore to ensure a required level of protection in these conditions. Controlled Droplet Application (CDA) has proved to be the most successful way of delivering pesticides at very low volume application. In the past, their use was found inefficient in arable crops essentially due to bad settings, such as inappropriate application rate, and problem of penetration of spray in cereal canopies. These spray generators may be, however, the best solution when treating small hydrophobic weeds because spray retention can be maximized and drift of smaller droplets minimized thanks to reduced droplet span. This study deals with blackgrass control in cereals while limiting environmental losses using properly set rotary atomizers. The droplet size and velocity were measured to characterize treatment efficiency. Results and discussions Rotary atomizers (Fig 2a) produce narrower droplet size distributions than hydraulic nozzles (Fig 2b) as it can be highlighted by a lower span defined by (V90-V10)/V50 (Table 1). V10, V50 and V90 indicates that 10, 50 and 90% of the volume of spray is in droplet diameters smaller than this value. Material and Methods A high-speed camera used in double exposure mode coupled to a LED backlighting records water droplets produced by a Micromax® 120 (Micron) at various flow rates and rotating speeds. Images were analyzed with a Particle Tracking Velocimetry Sizing (PTVS) algorithm developed in Matlab®. This atomizer was benchmarked to a flat fan nozzle. Conclusion and perspectives PTVS allowed a good characterization of droplet size distributions required for application method efficiency assessment. Reaching an optimal spray retention on weed surfaces while reducing the proportion of smaller droplets to reduce drift potential is a challenge that should rely on a reduced droplet span. Retention and drift are currently under investigation as a function of flow rate and rotating speed. Débit (ml/mn)V10 (µm)V50 (µm)V90 (µm) Span (V90- V10)/V50 2000 tours/mn 560 302 4045190.53 821 324 4435560.52 3500 tours/mn 560 221 3103980.57 821 249 3674740.61 5000 tours/mn 560 181 2713470.60 8211963064210.73 Teejet XR 11002 5601132083611.18 Hardi Injet 0155601773255141.03 Fig 3: Drop formation for a rotary atomizer Satelite droplets were observed in the spectrum of CDA sprayer but their percentage is low compared to flat fan nozzle (Fig 3). This phenomenon is gradually reduced when rotation speed is rised. Fig 2: Droplet size distributions: (a) Micromax (2000 rpm, 563 ml/mn), (b) Teejet (560 ml/mn; 1.4 bar) a b