THE INFLUENCE OF GRAZING FREQUENCY AND INTENSITY ON THE VIGOR OF LOLIUM-PERENNE L. UNDER SUBTROPICAL CONDITIONS

Lolium perenne L. (perennial ryegrass) exhibits poor persistence in su btropical environments. Grazing management may enhance the vigour and hence persistence of this species. Perennial ryegrass was subjected to various grazing treatments,and its vigour, indexed by etiolated growt h, was evaluated over 2 years. Pasture and individual tiller vigour we re monitored under 5 combinations of grazing frequency and intensity, applied rotationally, and 1 treatment of continuous grazing. The vigou r of infrequently grazed plots was greater than that of frequently or continuously grazed plots; however, grazing intensity did not influenc e vigour. Seasonally, vigour declined during mid (December and January ) to late (February and March) summer of the establishment year and fr om early summer (October) to autumn (May) during the second year. Poor vigour in frequently grazed plots was associated with low growth rese rves rattler than a lack of active tiller growth points. Towards the e nd of the second year, however, a lack of active tiller growth points also limited vigour in frequently grazed plots. Tillers from infrequen tly grazed plots (regardless of grazing intensity) had greater vigour than tillers from the frequently glazed plots. To enhance the vigour o f perennial ryegrass in subtropical environments, the frequency of gra zing should be reduced, particularly in summer.