Pasture systems to improve productivity of sheep in south-western Victoria. 1. Growth, composition, nutritive value and persistence of resown pastures
Geoffrey Saul A B D , Gavin Kearney A C and Dion Borg AA Department of Primary Industries, Hamilton, Vic. 3300, Australia.
B Present address: PSA Services, 98 Leura Lane, Hamilton, Vic. 3300, Australia.
C Present address: 36 Paynes Road, Hamilton, Vic. 3300, Australia.
D Corresponding author. Email: geoff.saul@bigpond.com
Animal Production Science 49(8) 654-667 https://doi.org/10.1071/EA06142
Submitted: 21 April 2006 Accepted: 25 April 2009 Published: 27 July 2009
Abstract
Two pasture systems were compared at five on-farm sites across south-western Victoria between 1990 and 1996. The ‘typical’ pasture treatment mimicked the pasture and grazing management common in the region, with volunteer annual-based pastures fertilised with around 5 kg/ha phosphorus (P) each year. The ‘upgraded’ pasture treatments were resown to phalaris, perennial ryegrass and subterranean clover, and higher rates of fertiliser (13–25 kg P/ha.year) plus other nutrients were applied. Both pastures were set stocked with the participating farmers breeding ewes. Stocking rate was an emergent variable on each plot. The stocking rate on the typical treatments was based on normal farm practise. Initially, the stocking rate of the upgraded pastures was 15% higher than for the typical pastures and increased over time depending if the ewes in the upgraded pastures were heavier than those in the typical pastures. Measurements included soil fertility, pasture production, nutritive value and composition, and animal production.
Net annual pasture production of the upgraded pastures was 10 500 kg/ha compared with 8700 kg/ha for the typical pastures. This average difference (18%) between the treatments was greatly influenced by the large advantage (40%) of the upgraded pasture in the wet year of 1992. Upgraded pastures had higher pasture production than typical pastures in spring but the reverse occurred in autumn. In a separate small plot experiment, the response of each pasture to higher P fertiliser applications was tested. In autumn and winter, there was a significant interaction between pasture type and P rate, with higher responses on the upgraded pastures. In spring, both pastures responded to increased P applications but the upgraded pastures were more responsive at all P rates. The upgraded pastures contained significantly higher legume content (30–50%) than the typical pastures (10–20%). The proportion of sown perennial grasses in the upgraded pasture declined from around 30 to 10% after 6 years displaced by annual grasses and broad-leaf weeds. Herbage from upgraded pastures had significantly higher crude protein content (2–7 units) and digestibility (1–10 units) than the typical pastures with the difference between the treatments increasing over time.
The set stocking policy used in this experiment is likely to have exacerbated the decline in sown perennial grasses and implementation of some form of strategic or rotational grazing may have improved persistence. The experiment also highlights the importance of selecting perennial grasses able to cope with the local environment and grazing conditions. Despite the decline in perennials, these results show significant potential to improve pasture productivity and quality in south-western Victoria.
Acknowledgements
Pivot fertilisers (now Incitec-Pivot) and the Department of Primary Industries funded this project. We would especially like to acknowledge the support provided by the late Don Rooney from Pivot fertiliser who was instrumental in getting the experiment underway. We also thank the farmers who allowed access to land, livestock and facilities on their farms. The farmers were the late Mr Alister McKenzie, ‘Hillside’, Ararat; Mr Barry Reader, ‘Ardwick’, Edenhope; Mr Sandy MacMillan, ‘Rockbank’, Lismore; and Mr and Mrs Robert Lyons, ‘Dundas Park’, Vasey. The Hamilton site was on the Department of Primary Industries research farm, managed by Brian Clark. We appreciate the assistance, goodwill and input the farmers provided during the project. We thank the many staff including Don Jowett, Lisa McIntyre, Tom Morgan, John Cayley, Phillip Forsyth, Paul Quigley, John Graham, Phillipa Noble and Martin Dunstan who provided field support and advice. Steve Clark provided assistance with the figures and Richard Stockdale provided helpful editorial input.
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