BUFFER ZONES FOR REDUCING PESTICIDE DRIFT TO DITCHES AND RISKS TO AQUATIC ORGANISMS

Pesticide drift from field sprayers fitted with different types of spr ay nozzles was investigated under various wind speed conditions. Dropl et drift was measured adjacent to the sprayed field, on the ditch bank , and in the ditch. Measurements were carried out in the normal spraye d situation and with an unsprayed buffer zone 3 or 6 m aide. The resul ts indicate that there are major differences between spray nozzles. Dr ift deposition increases,vith wind speed. In the sprayed situation and with a,wind speed of 0.5 m/s, there was a maximum of 6.0% drift depos ition halfway down the ditch bank and no drift deposition in the ditch . At 3 m/s wind speed these figures are 25.1 and 2.2%, respectively. A t 5 m/s wind speed, 7.2% drift deposition was measured in the ditch. R isk assessment (cf. SLOOTBOX model) carried out with 17 pesticides use d in the study area indicated that at this sind speed, 8 of the 17 pes ticides investigated posed a risk to aquatic organisms. Creation of a 3-m buffer zone decreases drift deposition in the ditch by a minimum o f 95%, Adjacent to the buffer zone only 4 of the 17 pesticides investi gated posed a (minor) risk to aquatic organisms. With a 6-m buffer zon e no drift deposition in the ditch could be measured (wind speed maxim um, 4.5 m/s). Creating unsprayed crop edges offers good possibilities for the protection of aquatic ecosystems. Socioeconomic research among farmers indicates that buffer zones, such as unsprayed cereal edges a nd unsprayed grass strips, could well be adopted in agricultural pract ice. (C) 1998 Academic Press