ASSESSMENT OF PERENNIAL RYEGRASS VARIETY COMPATIBILITY WITH WHITE CLOVER UNDER GRAZING

Four white clover varieties, of differing leaf sizes, were grown in bi nary mixtures with 33 perennial ryegrass varieties of differing maturi ty, ploidy, yield potential and morphological characteristics. Clover compatibility was assessed on the basis of white clover plant survival over a 2 year growing period under a rotational cattle grazing system . Tetraploid varieties were significantly more compatible with white c lover than diploids, with the early and intermediate tetraploids being the least aggressive towards clover. There was a two-fold range of di fference in clover survival between the grass varieties which weve the most and least aggressive towards clover. Under the conditions impose d, small leaved clovers survived better than larger leaved types. Asse ssment of grass variety production and morphological characteristics r evealed that sward density was the overriding factor determining grass /clover compatibility. Further examination by principal component anal ysis revealed that among the grass varieties, a growth pattern of high er spring rind lower summer yield potential was an additional factor c ontributing to high clover compatibility in this study. The value of t he methodology for identifying highly clover-compatible grass varietie s and its potential as a means of testing new grass and clover varieti es is discussed.