PM—Power and Machinery: Seed Loss when Cutting a Standing Crop of Oilseed Rape with Two Types of Combine Harvester Header

Abstract Oilseed rape has the potential to expand as an industrial crop. However, as oilseed rape matures, seed loss occurs by dehiscence of the seed from the pods prior to harvest and also as a result of crop disturbance by machinery during harvest. Seed loss of 600 kg ha−1, 25% of the recorded yield, is not uncommon. This directly increases the price for industrial users and can also reduce oil purity because volunteer plants in subsequent oilseed rape crops may have a different oil fatty acid profile. Oilseed rape plants also persist as weeds in subsequent crops. An experiment was carried out to identify the cause of, and quantify contributions to, seed loss from two different designs of header fitted to the combine harvester; a standard header and a header with a conveyor fitted behind the cutterbar, claimed to assist crop flow into the auger. Seed loss was measured using trays placed in the ripening crop prior to harvest. Seed shed before harvest, 11 kg ha−1, was low as a result of the relatively settled weather conditions. There was a significant difference between losses from the two types of header. The loss from each side knife was the same, but because of the differing header widths, translated into losses of 18·4 and 34·6 kg ha−1 for the conveyor-assisted and standard headers, respectively, showing the advantage of using a wider header in reducing this loss. Excluding shedding loss and side knife losses, seed loss from the conveyor-assisted header was 59 kg h−1 against 104 kg h−1 with the standard header. Loss caused only by the cutterbar of the conveyor-assisted header, 27 kg ha−1, was less than half that of the standard header cutterbar, showing the effectiveness of the combination of forward positioning of the cutterbar and conveyor-assistance. At 2001 costs, the conveyor-assisted header would recover its additional purchase price in five years if used to harvest 171 ha of oilseed rape per year.