Development of picking devices for chamomile harvesters

Abstract

German chamomile (Matricaria recutita L.) is cultivated throughout the world on about 20,000ha to obtain the inflorescences as raw material for drug production. Due to high labour costs, in industrial countries large-scale production is only feasible by mechanized harvest. It was concluded that in terms of quality of inflorescences and picking efficiency, rotating picking drums with comb sections achieve the best results. The authors prefer an increase of ground speed instead of a higher working width to achieve a higher productivity. The picking efficiency of existing flower harvesters is limited by the maximum drum rotation speed to ensure the discharge of picked inflorescences from inside the picking drum. To avoid this problem, new picking principles were developed and tested under field conditions. In a first version, double-blade combs with both a fixed and an oscillating layer were used for cutting the remaining stalks near the inflorescences. In a second version, shearing pins were attached for cutting the stems. A comparison under same field conditions resulted in advantages for the principle with shearing pins. To support the separation of cut inflorescences from the picking comb, despite the high drum rotation speed and therefore a high centrifugal force, in the first versions an air stream barrier was used, but with a limited effect. Under good crop conditions approximately 1hah−1 was harvested with a working width of 3m. A clear impact of ground and rotation speed on losses and quality of the harvested material could not be shown in the tests. To enable a comparison between an open drum with inside discharge and a closed picking drum with peripheral discharge, such a closed picking drum should be also designed, manufactured and tested in the next step.