Effects of Changes in Flax (Linum usitatissimum L.) Density and Interseeding with Red Clover (Trifolium pratense L.) on the Competitive Ability of Flax Against Brassica Weeds

A field experiment was carried out to evaluate the competitive ability of flax against Brassica weeds. Two densities of flax, either with or without red clover, and either with or without Brassica were sown. The presence of Brassica decreased seed yield for flax by 15–30%. The flax sown at the high density and interseeded with red clover improved the crop's competitive ability from the early growth stages. The early competition between flax and the weed was reflected in a smaller (about 30–50%) production of seeds and shoots in Brassica plants at the end of their cycle, which suggests a lower capture of resources when weeds did not grow alone. In one year, both high density and interseeding with red clover resulted in an increased capture of N by the crop and a reduced accumulation of N in seeds of Brassica. These findings indicate that the crop suppressed the growth of weeds, affecting future weed abundance.