Effect of Management on Leaf Growth and Senescence of Three Contrasting Grass Species

The innuence of continuous grazing management on leaf extension, leaf senescence and tiller density of 3 grass species with contrasting tillering rates, tiller size and growth habit was examined. Perennial ryegrass (Lolium perenne L. cv. Grasslands Nui), tall fescue (Festuca arundinacea Schreb, cv. Grasslands Roa) and Yorkshire fog (Holc,,s la11allls L. cv. Massey Bnsyn) were maintained in as near a steady state as possible at sward heights of 3-10 cm. The balance between leaf extension and senescence, and tiller density resulted in net extension per unit area being generally greatest at sward heights of- 5.5 cm in Yorkshire fog and ryegrass and IO cm in tall fescue. The relative insensitivity of ryegrass tiller density for up to 4 months after increasing sward height means that optimum sward height in ryegrass may increase to 10 cm during that time. In ryegrass and tall fescue, but not Yorkshire fog, there appears to be more scope for altering grazing height to achieve greater sward production in New Zealand than is apparent in studies with ryegrass in the UK