Static and dynamic distribution of spray from single nozzles and the influence on biological efficacy of band applications of herbicides

Spray distributions from different stationary nozzles were measured when adjusted to apply 20, 15 and 10 cm bands. As the distribution is influenced by the prevailing wind conditions and driving speed, the dynamic spray distribution of some of these nozzles was also measured. Spray losses were calculated as deviations from the optimal even-spray volume distribution in the band. The best distribution for band application was obtained using even-spray nozzles, whereas standard flat-fan nozzles and hollow-cone nozzles had an uneven distribution with a peak just below the nozzle centre and less spray towards the edges of the spray swath. In field experiments applying phenmedipham against Brassica napus as a model weed, the biological efficacy of the nozzles using the same bandwidth settings was compared with broadcast applications. There was a poor correlation between the measured spray distribution in the static test and biological efficacy in the field, which declined when the bandwidth was reduced to less than 20 cm. Reasons for this are discussed.