Competition between Canada Thistle [Cirsium arvense (L.) Scop.] and Faba Bean (Vicia faba L.)

This study was conducted to investigate whether density, above-ground biomass and nitrogen (N) concentration of Cirsium arvense (L.) Scop. cause serious reductions in faba bean (Vicia faba L.) yield. A 2-year field experiment (1991-93) with four Cirsium densities (0, 4, 16, 64 plants m-2) was carried out. Statistical analysis showed a significant effect of Cirsium density on faba bean yield. Multiple regression analysis showed that the main factors causing faba bean yield losses were the density and aboveground biomass of Cirsium. The results of this study demonstrate that Cirsium competition reduces faba bean yield. The mean faba bean yield losses over the 2 years were 10, 12 and 8% for above-ground biomass, seed and stem, respectively, for a Cirsium density of 16 plants m-2.