Competition in Mixtures of Herbage Grasses

Abstract

The yields at a number of harvests of 4 herbage grasses (2 cocksfoot varieties and 2 ryegrass varieties) were compared in pure stand, in all possible 50:50 mixtures at 2 densities (2 and 4 in. spacing) and under 2 different cutting regimes. Under one cutting regime (HS 1) the material was kept vegetative, in the other (HS 2) the plants were allowed to pass out of the vegetative phase before the 1st cut but were frequently defoliated thereafter. Neither density nor cutting treatment had any effect on total yield but cutting treatment had a marked effect on competitive performance of the different elements and also on the relationship between the yields of individual elements in pure stands and in mixtures. Under the cutting treatment HS 1 the 2 ryegrass varieties had greater "competitive ability" than the 2 cocksfoots and competitive ability tended to be associated with vigorous performance in pure stand, whereas under the conditions of HS 2 the cocksfoot varieties were competitively superior, one of them markedly so, and there was no obvious relationship between mixture and pure-stand behavior. The effects of density on competitive behavior were negligible in HS 1 and slight in HS 2. Mixtures tended to yield more than the mean of the yields of their 2 components.