Effect of sward cutting management on the relative performance of perennial ryegrass varieties

The performance potentials of six perennial ryegrass Varieties for conserva tion or grazing use were compared between 1994 and 1996 in N. Ireland. They were maintained, either under constant lax defoliation (conservation) or c onstant severe defoliation (simulated grazing) management for 3 years, or a nnually alternated between these two managements with the changeover taking place either in autumn or at the first cut of the following year. Starting one set with lax defoliation in the first year and the other with severe d efoliation created duplicates of these two alternating treatments. The resu lts showed that variety yield differed depending on the season and the mana gement imposed and there were differential responses to the various treatme nts. Conducting an alternating management system that implemented the manag ement change in autumn provided a valid estimate of yield performance poten tial for both simulated grazing and conservation use, compared to constant management systems. Although significant differences in variety ranking bet ween lax defoliation and severe defoliation management yields were only obs erved in the third year, the study showed that if the management change was implemented in autumn, the yield potential of varieties in the following y ear was not affected by the preceding year's management regime. Leaving a l onger sward (6 cm) to over-winter increased the spring performance of the V arieties in some years, compared to a shorter sward (3 cm), which may have implications for grazing management. There were also indications that impos ing an alternating management system might alter the absolute magnitude of the sward density ratings relative to a constantly managed system, though v ariety rankings would remain unaffected. It was concluded that the current alternating management testing system use d to evaluate candidate varieties for UK National or regional recommended l ists, does not cause any variety to be unfairly advantaged or disadvantaged .