Replacement series experiments make possible the study of inter and intraspecific competition, based on the fact that the yield of the species under competition can be determined by comparing with plants in monoculture. The objective of this work was to investigate the relative competitive ability of wheat crop with the weeds Italian ryegrass or wild radish. Three experiments were conducted under greenhouse at UFPel, in 2006. The treatments were conducted in a completely randomized design, with four replications, with the treatments arranged in replacement series. The proportions of wheat plants and competitors Italian ryegrass or wild radish were: 100/0, 75/25, 50/50, 25/75 and 0/100, always with a total population of 900 plants m-2. Competitiveness statistical analysis consisted in applying diagrams to the replacement series and interpreting the competitiveness indices. The competitive relationships between wheat and ryegrass or between wheat and wild radish plants are altered by the proportion of plants that compose the association. Wheat shows superior competitive ability to ryegrass but inferior to wild radish when the species have similar proportions of plants in the associations and when these species occur in the same ecological niche.
competition; mutual interference; replacement series
