Project Summary
Six certified organic farmers and one conventional farmer tested three weed management strategies for flax at nine sites in 2005 and 2006. Drilled flax with no underseeding was compared to flax grown with alfalfa and with red clover underseedings. Flax grain and oil yields, omega-3 fatty acid content and weed growth were measured. Flax yields, measured by hand harvesting, differed due to underseeding and were 1,634 lbs/A where no underseeding was planted, 1,510 lb/A with alfalfa underseeding and 1,484 lb/A with red clover underseeding. Machine-harvested yields were approximately 20 percent less than hand-harvested yields. Slight differences in flaxseed oil content due to underseedings were not economically significant. Underseedings did not suppress weed growth during the flax growing season, but legume underseedings were effective at suppressing weed regrowth 60 days following flax harvest. Red clover provided the most biomass regrowth, 1,692 lb/A, and alfalfa produced 1,043 lb/A. Where flax was grown without an underseeding, weed growth was greatest both before and after flax harvest. Results are similar to those from research trials at two Iowa State University experiment stations in 2005 and 2006. Results indicate that seeding legumes with the flax crop does not provide much competition with weeds until after the flax has been harvested. By late summer, established legume stands are very effective at preventing weed regrowth.