Influence of nozzle type, nozzle arrangement and side wind speed on spray drift as measured in a wind tunnel

Spray drift is a great concern because of environmental consequences of agricultural practices. Many studies were conducted in wind tunnel (Miller, 2011; Nuyttens, 2007; Herbst, 2003) mainly focusing on the definition of quantitative deposition on collectors at different distances or heights according to (ISO 22856, 2008). In most cases, only one nozzle positioned frontally (wind direction perpendicular to the main axis of a Flat Fan spray) is tested. This study was carried out in IRSTEA wind tunnel that includes a 9 m distribution test bench. A short boom of 4 nozzles (50 cm spacing, 60 cm height) was oriented in either lateral or frontal position. The effect of wind speed (2, 4 and 7.5 m.s), nozzle type (including mix types) were studied. Nozzle types were FF110 02 (Albuz AXI), air injection FF (Albuz CVI) 110 02, and air injection twin jets (Albuz CVI Twin) 110 02 and were used at 2.5 bar. Different nozzle arrangements represented 18 tests in lateral position and 21 in frontal position. Deposition values every 5cm are processed with an inverse cumulative calculation. Results are expressed in terms of (i) the cumulated amount of drift (ii) drift values at 5m (minimum buffer zone width in France). Results logically showed that an increase of wind speed leads to an increase in lateral spray drift values for all modalities. Results confirmed that drift reduction classification of nozzles based on lateral or frontal measurements are not comparable (Douzals, 2012). In frontal position, the number of nozzles induced a cumulative effect on spray deposition without protective effect between collateral sprays. In lateral position, CVI and CVI Twin nozzles involved less drift amount compared to AXI nozzles. Drift values were reduced when replacing the first or the two first AXI nozzles -that are most exposed to the windby a CVI or CVI Twin. However, drift mitigation ratio was better for the CVI Twin compared to CVI nozzle. These results will contribute to a wider study on interactions between sprays types & position and their potential contribution to drift or drift mitigation.