F.R. McKENZIE

Department of Grassland Science, University of Natal, Scottsville, Republic of South Africa

Abstract

Poor persistence of Lolium perenne (perennial ryegrass) in subtropical environments has limited its use in intensive animal production systems. Inadequate grazing management principles are often cited as contributing to poor persistence in perennial ryegrass. Tiller density and persistence of perennial ryegrass were monitored for 2 years under 6 combinations of grazing frequency and intensity. Within any season, the persistence of tillers grazed frequently and intensively was lower than that of those grazed infrequently, irrespective of intensity. Overall, tillers initiated in early summer of the establishment year (Year 1), autumn, winter and spring were important in helping maintain perenniality, while those initiated during mid- to late summer of Year 1 and early to late summer of Year 2 were not. Tiller densities declined during summer and increased during autumn, winter and spring. In Year 1, tiller density ranged from 6 670 (late summer) to 14 460 tillers/m² (spring) and in Year 2 from 4 440 (late summer) to 15 970 tillers/m² (spring). To enhance the persistence of perennial ryegrass under subtropical conditions, managers should graze their pastures infrequently, particularly in summer.