Open access publications in the SLU publication database

Abstract

The investigation was conducted as a part of the requirements for a Masters Degree in Agriculture at the Swedish University of Agricultural Sciences. The work is a result .of cooperation between the Department of Agricultural Engineering and The Swedish Sugar Company. Earlier Swedish investigations have indicated that band spraying with small volume rates (30-60 l/ha) can produce a result as good as when spraying with conventional volume rates (about 200 l/ha). Therefore, there is an interest to find an equipment able to distribute small volume rates of spray in a reliable way. The intention was to compare a new Swedish air-turbine-powered rotary atomizer to two other rotary atomizers, two flat fan nozzles and one air atomizing nozzle in band spraying in sugarbeet. The nozzles were used in two field trials with different combinations of spray rates, liquid pressure and, where appropriate, air pressure. The trials were conducted in order to elucidate differences in biological effect. The differences were small and only in some cases significant. There was however a tendency towards better and more even effect to the overall spraying with SS 11001 which was included as a comparison. Droplet size was determined with a laser instrument and the results were in very good accordance with what one can expect when varying pressure, flow rate and measuring point in the spray. All the centrifugal nozzles gave a more narrow drop size spectrum than the hydraulic nozzles, though partly dependent on where the measurement was carried out in the spray. The air atomizing nozzle gave a droplet size as small as 50 m. A comparison of treatments with the same amount of spray, i.e. the same herbicide concentration, does not distinctly show better weed control of small droplets than of big ones. The air-turbine-powered rotary atomizer showed some technical disadvantages. Disc rotational speed varied a lot and the screening caused drop. The air atomizing nozzle was very sensible to contaminations in the spray and was easily clogged up. Girojet was not very well suited for band-spraying due to the wide spray angle.