Experiences with different methods of harvesting borage (Borago officinalis L.)

Borage seeds (Borago officinalis L.) are an important source of gamma linolenic acid (GLA), which plays a significant role in pharmacy and nutrition. The mechanisation of the harvest of borage seeds is a weak point of the cultivation technology. Gradual ripening and strong scattering make mechanised harvesting difficult. In addition, the seeds are damaged by mechanical stress during harvest and post-harvest processing. In 2000-2002, different harvesting methods were tested with several blue and white flowering borage accessions on experimental plots in Finland. The harvesting methods resulted in the following minima and maxima of seed yield, fatty oil content of the seed oil and GLA content of the seed oil: a) manual harvesting and manual seed separation: 578-880 kg/ha, 35.8-33.7% and 22.9-26.5%; b) swath reaping, 7 d indoor post-harvest ripening and manual seed separation: 165-702 kg/ha, 29.2-33.1% and 19.0-32.4%; c) swath reaping, 7 d outdoor post-harvest ripening and combine threshing on the field: 131-259 kg/ha, 29.2-33.9% and 23.0-24.4%; d) direct combine threshing on the field without a post-harvest ripening period: 145-178 kg/ha, 29.6-32.3% and 19.9-18.2%. As the individual harvesting methods were tested in different years, a direct comparison was not possible. The seed yield of the white flowering forms exceeded the yield of blue flowering accessions in every case. None of the tested mechanised harvesting methods allowed the extraction of a satisfactory fraction of the seeds. Therefore, designing effective harvesting methods will be the most important prerequisite for profitable borage production in the future.