Use of non-sprayed buffer zones is a widely used method to protect sensitive objects within or adjacent to fields treated with pesticides. These buffer zones should protect the objects from pesticide residues caused by spray drift and leakage. The use of untreated buffer zones has been mandatory for Swedish farmers since 1997. E.g. recommended minimum safe distances to sensitive areas for spray situations are 12 m to wells, 6 m to streams, ponds or lakes, and 1 m to ditches and drainage wells. Studies have shown that buffer zones are not always respected and that there is a need to improve the protection of sensitive objects. On a typical sprayer, all nozzles on a section of the boom are either on or off. A higher resolution in sprayer control would reduce the untreated area but still be able to respect the buffer zones. German and Dutch research have shown how GNSS-controlled (Global Navigation Satellite System) application of pesticides can be targeted to defined areas in the field. GIS (Geographic Information System) was used to define the areas to be sprayed. The objectives of this study were to develop and evaluate a system that automatically could shut off single nozzles along the spray boom to avoid pre-defined areas in the field. Such a system could improve management of buffer zones, reduce the risk for mistakes and improve record keeping from spraying activities. At the time of project start, there were commercial controllers that could fulfil parts of the requirements involved in the project. A commercial spray controller, Legacy 6000 (Teejet), could consider pre-defined areas by using the field boundary features. During 2006 and 2007, the system was used in practice on a conventional trailed sprayer with a 24 m boom and 7 boom sections. Experiences from mapping and spraying were documented. Also accuracy of the system was studied in an experiment using video recorder and analysis of the video frame by frame. Results were communicated with several manufacturers of sprayer controllers to improve development of coming products. The following season, 2008, a small sprayer with a 6 m boom and individual nozzle control was constructed. This year, the study of accuracy focused on small circular buffer zones, e.g. close to drainage wells. Spraying was done on an asphalt surface during a sunny day, leaving wet and dark marks when nozzles were activated. The whole buffer zone was photographed directly after spraying, and the pictures were later analysed manually to determine the accuracy of the sprayer. Different controller settings, spray nozzles and GPS receivers were used. The accuracy of a conventional sprayer with DGPS was found to be about +/- 1 m. Accuracy of the sprayer with solenoid valves and RTK GPS was about half of this, i.e. +/- 0,5 m. This is probably better than the possibilities with manual control. Different methods for mapping fields and creation of boundary files were evaluated and compared. Mapping could be done through digitalisation of an aerial photograph or when spraying the field for the first time. Best accuracy is achieved if mapping could be done with a RTK GPS on e.g. an ATV. A method for calculation of double-sprayed area has been developed in the project. The mapped fields in the project have served as a base for a simplified tool that can be used by farmers and advisors to determine the advantages with more accurate sprayer control. In general terms, a farmer can save 1-5 % of the pesticide cost if a GNSS-controlled sprayer with individual nozzle control is used, instead of a conventional sprayer. The project sprayers have been demonstrated on several field shows and other activities with farmers. The number of controllers for automatic boom control on the Swedish market has increased during the project time
