Edmonds, A. S.Thom, Errol2026-04-012026-04-011984https://hdl.handle.net/10289/18170A series of trials investigated the contribution of introduced grasses (Lolium perenne and Bromus catharticus) to seasonal production of a high yielding dairy sward containing paspalum (Paspalum dilatatum). The persistence of the introduced species was also determined. Autumn overdrilling improved (<500 kg DM/ha) herbage production in the following winter/spring and autumn, but thereafter differences between drilled and undrilled swards disappeared. The monitoring of individual plants showed that there were high summer losses of introduced plants; up to 56% were lost by one year after drilling. The contribution of Bromus catharticus to herbage mass was less than that for Lolium perenne, as summer losses of the former plants were higher than for the latter because of increased susceptibility to direct ‘animal effects’ (eg. ‘pulling’). Bromus catharticus was therefore excluded from subsequent experiments. Summer growth of introduced plants was more restricted when they were closely associated with established paspalum than with other resident species, and large plants had better summer persistence than small plants. Manipulation of the light environment of the introduced ryegrass plants by regular clipping (10 mm stubble) of surrounding resident herbage markedly improved their ability to survive summer management and environmental stresses. The introduced plants were able to attain a large average size (20 to 50 tillers per plant) before the onset of summer. Summer losses of introduced plants were higher when grazed at a short (2-3 week) rather than a long (3-4 week) interval and if paspalum was a close neighbour. About 20% of total losses were related to direct cow damage, namely, severe grazing, ‘pulling’, dung and urine deposition, and trampling. The latter effects may be important where stocking densities are high. Other treatments such as late-winter/early-spring application of nitrogen fertiliser and irrigation during summer/autumn, failed to improve persistence of introduced ryegrass. One of the various ecological strategies that gives paspalum a competitive advantage over ryegrass is its ability to accumulate large reserves of carbohydrate. Measurement of nonstructural carbohydrate accumulated in above-and below-ground organs indicated that these reached a maximum for both species towards the end of the period of their most active growth. At this time the nonstructural carbohydrate level for paspalum at 1050 kg/ha, was four times greater than that for ryegrass. Possible practical methods for improving the persistence of ryegrass introduced into established swards are discussed.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis