The measurement and analysis of competitive ability among populations of white clover and perennial ryegrass.

Analysis of the competitive interactions among a set of white clover and perennial ryegrass populations indicated that the intra-specific pressures exerted by the white clover plants upon themselves were significantly greater than the inter-specific pressures they exerted upon the perennial ryegrass. This partitioning of competitive effects could not be carried out on the ryegrass populations, however, because the data required the fitting of separate models to monocultures and duocultures. Although not significant at this stage of the experiment, trends were detected among some of the clover-ryegrass duocultures that could be related to their previous coexistence. The results are briefly discussed in relation to the problems surrounding the measurement of competitive effects among species that ideally require very different managements.