Coexistence and the productivity of white clover-perennial ryegrass mixtures.

Yield comparisons between five white cloverperennial ryegrass mixtures, whose individual components had previously coexisted, and a corresponding set of ten mixtures based on components that had not coexisted disclosed a yield advantage to the former group of 8.5% over a 4-year period. All five clover populations produced their highest yields when associated with their coexisting grass. The coexisting mixtures also yielded more grass in spring, probably due to the exotic origin of the majority of the companion grasses, reinforced by the nitrogen transfer process between clover and grass. The relative proportions of clover attained by the five populations was apparently unaffected by grass companion. These results are briefly discussed in the context of improving the productivity of white clover-perennial ryegrass mixtures.