Different clipping intensities and intervals were applied to plots of mixed perennial ryegrass (Lolium perenne) and subclover (Trifolium subterraneum) in this study to determine the effects of different grazing management strategies on improved pastures containing these species. During this three year study perennial ryegrass cover decreased and subclover cover increased in defoliated plots, regardless of stubble height and defoliation interval, while in undefoliated plots, both species declined and annual grasses increased. Stubble height did not affect any of the measured parameters but defoliation interval was important. The density of perennial ryegrass plants at the end of trial in 1983 was highest when plots were defoliated once every 21 or 35 days compared to those defoliated every 7 days, 49 days, or the undefoliated control plots. Root biomass per plant, however, increased linearly as defoliation interval increased from 7 to 49 days between defoliation events. Viewed together, these data suggest that under-utilization of grass-clover pastures may be potentially as damaging to pasture persistence as overutilization.
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