Determination of the influence of the driving speed on the application parameters of orchard sprayers

Abstract

Orchard sprayers with air transported fine droplets need an exact adjustment of the airflow and the spray nozzles in order to reduce the drift of pesticides. The adjustment is made on one hand side by the manufacturer and on the other hand side by the farmer in the orchard by choosing the tractor speed, the PTO shaft rotation speed and the pump pressure. For testing two test beds have been in charge in the region of Styria since almost 2 decades. One of them is able to measure the flow field in a vertical plane representing the tree row in a distance of approx. 1.5 m from the middle of the track. The second measures the water distribution in the same vertical plane. Both are stationary so that the influence of the driving speed can hardly be assessed. High driving speeds up to 12 km/h and the increasing height of the orchards impose additional uncertainties. This was the reason for the present research project, which was intended to investigate the influence of the driving speed. A new air flow measurement test bed has been build, which is able to measure the flow field also during tractor movement in the described vertical plane up to 5 m above ground. Four different sprayers have been investigated in an orchard with and without leaves by visual method for four different speeds to determine the optimal application parameters. The same sprayers have been tested with the moveable flow field test bed. Results show a reasonable correlation between the measurements for all investigated speeds. The differences between the sprayers are evident, nevertheless a method has been found to deduce the correlation between the stationary measurement and the optimal parameters for the orchard. So the stationary flow test bed can be directly used to develop sprayers.