AbstractSeasonal trends among those characters, affecting productivity in white clover‐perennial ryegrass mixtures were investigated m a set of 20 mixtures using clover material derived from a. diallel cross between four contrasting white clover varieties. The productivity and associated vegetative characters showed the familiar pattern of high grass production in spring, and early summer, with a secondary peak of growth in autumn, whilst clover achieved its; highest productivity levels in mid‐summer. A significant linear relationship was established between clover canopy height and ryegrass canopy height for all 20 mixtures. Although no significant heterogeneity was detected among the fitted regression lines, there was an indication that the linear regressions provided a better fit to the data in those mixtures having ‘Skomer’ as the grass companion. An analysis of the differences in canopy height between ryegrass and clover indicated that the ‘Menna ‘/’S. 23’ mixture had a reduced seasonal range compared to the other mixtures. Consequently, during the early par', of the growing season, when the tallest canopies occurred and. when shading of clover by the grass was most intense, the difference in canopy height between ‘S. 23’ and ‘Menna’ was relatively low. There was a pronounced effect of grass companion upon canopy height difference, due entirely to the taller growth habit of the ‘Skomer’ ryegrass variety, These interrelationships are discussed briefly in the context of improving the productivity of white clover
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