Contact: Drift from boom sprayers 2. Wind tunnel experiments To measure airborne and fallout spray deposits of different spray application techniques in a wind tunnel under different conditions To calculate the drift potential of different spray applications using contrasting approaches and compare these results with the reference spraying D NUYTTENS 1, M DE SCHAMPHELEIRE 2, K BAETENS 3 & B SONCK 1 1 Institute for Agricultural and Fisheries Research (ILVO), Technology & Food, Agricultural Engineering, Belgium 2 Department of Crop Protection, University Ghent, Belgium 3 MeBioS, Department Biosystems, Catholic University of Leuven, Belgium Measuring set-up  Silsoe Research Institute wind tunnel facility  2 mm polythene collector lines → downwind spray deposits 6 horizontal lines (H 1 → H 6 ): fallout spray deposits 5 vertical lines (V 1 → V 5 ): airborne spray deposits  Spray liquid: Sodium fluorescein tracer (0.02%) + surfactant Agral (0.1%) Objective Materials and Methods Results Nuyttens D Drift from field crop sprayers: The influence of spray application technology determined using indirect and direct drift assessment means. PhD thesis nr. 772, Katholieke Universiteit Leuven. 293 pp. ISBN available at: Fallout & airborne deposits Spray application techniques: Measuring protocol  Single and static spray nozzle (10 s spraying) m nozzle height  Uniform wind tunnel air speed of 2 m.s -1  Environmental conditions: RH > 90%; T= 20 °C  Hardi ISO F reference nozzle at 3 bar to check for the repeatability  Spray deposits expressed as µL spray recovered from the lines for every liter of spray solution emitted by the nozzle  45 experiments Drift potential reduction percentages (%) Fallout deposits for different Hardi ISO nozzle types and sizes at 3.0 bar DPRP V1, DPRP V2 and DPRP H values (+ 95% confidence intervals) for different Hardi ISO nozzle types at 3.0 bar Results show the expected fallout and airborne deposit profiles  Highest deposits closest to the nozzle and a systematic decrease with distance from the nozzle.  Highest deposits at the lowest collectors with a systematic decrease with increasing heights For the same nozzle size (and pressure): DPRP air inclusion > DPRP low-drift > DPRP standard flat fan The bigger the ISO nozzle size, the higher the DPRP values for the standard and the low-drift flat fan nozzles at a constant spray pressure Standard flat fan nozzles: DPRP V1 > DPRP V2 > DPRP H Low-drift flat fan nozzles: DPRP V1 < DPRP V2 < DPRP H References Taylor et al., 2004 Drift potential (DP) & Drift potential reduction percentages (DPRP, %)  DP of the different spray appilcations calculated following 3 approaches: DP V1 : first moment of the airborne deposit profile DP V2 : surface under the airborne deposit curve DP H : surface under the fallout deposit curve  DP values are compared with the equivalent results from the reference spraying → DPRP V1, DPRP V2, DPRP H  DPRP values express the % reduction of the drift potential compared with the reference Conclusions Important in the interpretation of wind tunnel data for different nozzle types and sampling methodologies