THE EFFECTS OF MANAGEMENT AND PLANT VARIETY ON THE COMPOSITION, VERTICAL STRUCTURE AND STOCK-CARRYING CAPACITY OF LOLIUM-PERENNE TRIFOLIUM-REPENS PASTURES

The effects of sheep grazing, with or without a 7-week rest period before ear emergence, on species balance in four perennial ryegrass/white clover swards were assessed. Swards of an early (Aurora) or a late (Melle) flowering ryegrass were grown with either a small-leaved (Kent) or a medium-leaved (Milkanova) clover. The clover lamina, expressed as a proportion of the total lamina mass, was greater with Kent than Milkanova. This proportion was not changed by resting the Aurora (earlier rest) swards, but was increased by resting the Melle (later rest) swards. A greater proportion of the clover lamina mass was near the top of the canopy in the Milkanova than in the Kent swards, and during the summer than in spring or autumn. The densities of clover growing points were greater in the Kent than the Milkanova swards and were increased by the late rest period. This effect persisted over the winter. Stocking density was higher on the Kent than the Milkanova swards. The effects of the two rest periods, and the variety combinations, on pasture composition are interpreted as being principally a result of the differences in temperature between the earlier and later rest periods and of the different relationships between temperature and the growth of ryegrass and clover. Varietal characteristics, such as the vertical distribution of laminae, were also shown to be important.