Effect of harvest date and cultivar maturity on the composition of newly sown perennial ryegrass (Lolium perenne L) mixtures

Fluctuations in genotype frequency were followed, by electrophoresis, in a tertiary and three binary mixtures of ryegrass cultivars (Gremie, Morenne and Perma) grown in conventionally sown swards, under a silage-management system. By using this methodology changes in variety composition were monitored. In each mixture, the earlier heading component predominated at the first cut, the later flowering component at the second, with competitive advantage returning to the early component in the remaining cuts. Varying the timing of the first cut influenced this general pattern of competitive ability and revealed an interaction between timing of cut and cultivar maturity. The herbage from an early first-cutting date had, as its highest proportion, the earlier heading component of the mixture at the first cut, but the lowest at the second and subsequently an increased dominance towards the end of the season. Delaying the first cut reduced this advantage for the earlier component at that cut but resulted in its contribution being increased at the second cut and also in the subsequent cuts. The greatest dominance of one component over another at any cut was always associated with the largest differences between cultivars in their maturity, suggesting that stability might be lower in such mixtures.