ANALYSES OF YIELD FROM A COMPETITION TRIAL WITH PERENNIAL RYEGRASS

Four varieties of perennial ryegrass, (S24, S321, S23 and Endura), were grown in monoculture and in all possible binary mixtures. Three spatial arrangements of varieties within mixtures were used. Total DM yields were recorded from nine harvests during 1969 for mooocultures and mixtures and for the mixture components. The arrangement of varieties within mixtures had no effect on the total DM yield of the mixtures. Monocultures and mixtures did not differ significantly in yield at any harvest or in annual total, bnt there were differences between monocultures at some harvests. No differences between mixtures were detected. The experiment took the form of a competition diallel in which monocultures corresponded to the parents in a genetic diallel and mixtures to the crosses between these parents. There was a significant interaction hetween the rows (i.e. main variety effects) and the columns (i.e. associated variety effects) of the diallel table only at the first harvest. The change in the competitive ability of the four varieties throughout the season was examined. The relative ranking order of varieties for competitive ability altered as the season progressed.