Species competition in establishing swards: Suppression effects of ryegrass on establishment and production of associated grasses and clovers

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Abstract
Ryegrass suppression of cocksfoot (Dactylis glome rata L.), timothy (Phleum pratense L.), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.) was investigated in establishing; swards on soils of high and medium fertility. Eight rates, of perennial rye grass (Lalium perenne L.) and short-rotation rye grass (Lalium perenne L. × Lolium multifiorum Lam.), ranging from nil to 30 lb/ac were sown with a basal mixture of cocksfoot, timothy, and clovers. Sward composition, density, and production were recorded for two-and-a-half years. Results showed that cocksfoot and timothy were suppressed to a great degree by a high seeding rate of ryegrass, and even a relatively low seeding of 5 lb/ac caused considerable suppression. The effects persisted for the duration of the trial, although they were more severe during early establishment. Ryegrass suppressed the clovers, particularly white clover, during early establishment, but, once the growth of ryegrass tapered off, the clovers grew rapidly. and for the two-and-a-half-year period clover yields were similar in all treatments. During the initial establishment phase, the treatments sown with high rates of ryegrass were most productive, but in later periods total yields showed little variation between treatments despite marked differences in sward composition. The mixture sown without ryegrass was very slow to establish, but once established was only slightly less productive than the mixtures which included ryegrass. On soils of medium fertility the suppression effects, of ryegrass were less than on high-fertility soils, but the pattern of suppression was similar. Under high fertility short-rotation ryegrass was more aggressive than perennial.