Performance characteristics of air-assist nozzles
Air-assist nozzles mix air with the spray liquid and help transport the spray to the target. These nozzles make it possible to reduce application rate and still be able to provide adequate coverage while minimizing spray drift. Air-assist nozzles are relatively new for agricultural spraying and evaluations to date are limited. The performance of air-assist nozzles (Spraying Systems Airjet) were explored and the nozzles were evaluated in field tests using systemic and contact herbicides. Spray-drift assessments for the Airjet nozzles were also conducted. Application rate varied between 30 l/ha to 200 l/ha for the field tests and the spray-drift assessments. For most of the tests two different pressure settings were used. The overall conclusion for the Airjet nozzles is that the choice of air pressure and liquid pressure are very important in determining an acceptable spray pattern, droplet size spectrum and in minimizing spray-drift. The field studies with systemic and contact herbicides did not result in significant differences among the application rates. A spray volume of 30 l/ha gave poor control in the field studies and in the spray-drift assessments. Control improved dramatically with spray volumes above 50 l/ha. Different size inserts and different air and liquid pressures determine the spray volume. It was observed that different size inserts to the air-assist nozzles should be choosen rather than changing pressures if an entirely different spray volume is desired. Changing pressures affect the droplet size distribution and spray pattern uniformity a great deal. The characteristics of a ULV air-assist sprayer (AAN) were also explored. No field tests were conducted with this sprayer. The AAN-sprayer was not evaluated sufficiently to express extensive conclusions. A major observation was that the AAN-sprayer produces a non uniform droplet size distribution in the spray fan and has a high variation in the spray distribution. These studies indicated that air-assist nozzles have potential for applying pesticides at low spray volumes, provided that the air pressure and liquid pressure are maintained sufficiently low.
air-assistance; nozzles; drift study; field test
Rapport - Sveriges lantbruksuniversitet, Institutionen för lantbruksteknik
Publisher: Institutionen för lantbruksteknik, Sveriges lantbruksuniversitet
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