The design and testing of shields to reduce spray drift

Abstract

Drift, which is defined as the movement of chemical away from the intended target, is one of the major concerns in pesticide spraying, causing environmental pollution and economical losses. One of the major factors influencing drift is wind. Mechanical shields have been used as a method to reduce drift by deflecting wind away from the spray. In this study mechanical shields for minimizing spray drift were designed, developed and tested in a wind tunnel. Two different designs were considered and their performances were compared with the shield designed by Ozkan et al. (1997)--Each shield was tested using two standard flat fan nozzles (8001 and 8003), operated at three levels of pressure (138, 276 and 414 kPa) Test for no shield and no wind conditions were also conducted to represent zero drift condition. The average wind tunnel air velocity was 6.2 m/s. A three dimensional patternator (1.3 m x 1.0 m x 0,15 m) was used to measure the amount of spray recovery under each treatment. Percent spray drift and distance of center of mass from nozzle axis were used as criterions to compare the performances of the shields. Data was analyzed using a completely randomized design, and means separation was performed using Duncan's Multiple Range Test at 0.05 level of significance A symmetrical triple circular shield had the best performance compared to the other shields due to its aerodynamic features, which provided natural air assist as well as an air curtain in front of the discharge with partial shielding of the portion part of the nozzle. Results showed that shields are more efficient in reducing drift using the 8001 nozzle. The DL and percent drift values were not significantly consistent.