Spray liquid distribution and biological efficacy of commercially available nozzles used for precision weed control

The aim of this study was to test the application accuracy of commercially available hydraulic nozzles for the purpose of applying herbicides to decimetre sized cells. Based on various technical performance tests, 3 nozzles were selected for further biological efficacy tests. From the technical tests, nozzle output and nozzle height to achieve a 100-mm-wide spray swath were determined. In biological tests, efficacy and application accuracy controlling Matricaria perforata at the cotyledon stage with glyphosate in 100mm 100 mm
cells were tested. Efficacy was measured inside the square, in the border zone and just outside the square. The study showed that with commercially available nozzles, it is possible to apply a herbicide to a 100 mm 100mm cell at an application speed of 1-2m/s with a high precision and with only a limited proportion of the spray being lost outside the intended target area. The biological efficacy obtained in the central part of the cell was slightly reduced compared to a broadcast application. A tracer study revealed that this could be explained by a reduced nozzle output compared to the measured output in the technical test. The reduction was probably caused by a much shorter nozzle operating time during application to the cell. The valves used in this study therefore should be replaced with faster acting valves.