The effect of droplet characteristics on spray drift

Spray drift continues to be a major problem in applying agricultural pesticides (De Schampheleire et al., 2006). Factors that affect spray drift include the weather (Threadgill & Smith, 1975; Craig et al., 1998; Nuyttens et al., 2006 a), the physical properties of the spray solution (Buttler & Bradley, 2002) and the spray application technique itself (Miller & Smith, 1997; Ghosh and Hunt, 1998; Van De Zande et al., 2000, Nuyttens et al., 2006 b). One of the most important spray application factors are the nozzle type and spray pressure which determine the produced droplet size and velocity spectra (Heijne et al., 2002; Klein & Johnson, 2002). These characteristics affect the structure of the spray deposit and the biological efficacy. In addition, the characteristics of droplets determine their driftability (Taylor et al., 2004). Over the last years, several techniques using laser instrumentation have been developed to determine droplet characteristics like laser diffraction (Malvern laser) (Buttler Ellis and Bradley, 2002), the optical area probe technique (Particle Measuring System) (Combellack et al., 2002) and Phase Doppler Particle Analyzer (Aerometrics) (Farooq et al., 2001; Nuyttens et al., 2006 c). In this paper, on the one hand droplet characteristics and on the other hand drift characteristics in field conditions of different nozzle-pressure combinations are measured and compared using a PDPA laser based measuring set-up and a field drift measuring set-up.