Competition in mixtures of herbage grasses.
Plants of Ayrshire and Scotia perennial ryegrass and of Daeno II and Scotia cocksfoot spaced 2 and 4 cm apart were grown in boxes in pure stand and in all possible binary combinations, and first cut while still vegetative or at heading, and frequently cut thereafter. Neither density nor cutting treatment had any effect on total yield. When the first cut was at the vegetative stage the 2 ryegrasses had greater competitive ability than the 2 cocksfoots and competitive ability tended to be associated with vigourous performance in pure stand. When the first cut was allowed to head, the cocksfoots were competitively superior, particularly Daeno II, and there was no obvious relationship between mixture and pure.stand performance. Effects of increased density on competitive behaviour were negligible where heading did not occur and slightly favoured the rye. grasses where it did. Mixtures tended to yield more than the mean of the yields of their 2 components, and differences between cutting regimes were smaller than in the pure stands.-R. B.