A field experiment was conducted to evaluate the ability of two wheat cultivars to compete with ryegrass (Lolium multiflorum L.), and to estimate the competition effects of various densities of this species on the crop, at the Agronomy Experimental Station, in Guaiba, RS, during the 1978 wheat growing season. Two wheat cultivars ('E-7414' and 'PAT-7219') were grown in competition with ryegrass at the densities of 0, 130, 210, 470, and 750 plants per m'. The competition effects were maintained during the whole wheat cycle. Depending on the weed population, ryegrass competition caused significant decreases, varying from 18 to 56%, in seed yield of the wheat cultivar `E-7414'; whereas, for `PAT-7219' cultivar, although seed yield reductions varied from 4 to 22% , were not statistically significant. Ryegrass dry matter production increased proportionally to its population. However, ryegrass dry matter yield was significantly lower whe n this specie s competed with 'PAT-7219' wheat cultivar than with 'E-7414'. As an average for the established densities, ryegrass dry matter produced in competi tion with 'PAT-7219' was 31% lower than that obtained with 'E-7414'.
competition; wheat; cultivars; Lolium multiflorum; ryegrass