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Annual and perennial pastures react differently to autumn-winter grazing management

D.R. Kemp, P.M. Dowling, D.L. Michalk, G.D. Millar and M. Goodacre

NSW Agriculture, Agricultural Research and Veterinary Centre Forest Road, Orange NSW 2800

Premature decline in productivity is a major problem with improved pastures. Cost of re-sowing pasture can vary between $100-200/ha in high rainfall areas which does not include the opportunity cost incurred through production losses. An investment of this size must be carefully considered and needs to be protected through good management. At current costs and returns, for a merino sheep enterprise, an improved pasture must remain in a productive state for 8 to 10 years just to break even on the investment. Rather than replacing the pasture completely, it makes more financial sense to renovate the pasture using grazing management, fertiliser and, or pesticides. This can be achieved provided the pasture contains a reasonable nucleus of desirable species. Strategic grazing is an under-utilised, low-cost option which producers can use to manipulate pasture composition. Experiments at two sites in central NSW compared the effects of resting the pasture in autumn or winter on the botanical composition of annual and perennial pastures.

Results

In annual pastures, autumn or winter rests doubled legume content. Annual grass yields were a little greater than on continuously grazed plots, but reduced tillering of grasses provided more space for legume growth. In perennial pastures, rests during autumn and winter increased the proportion of perennial grasses over annual grasses to a small, but significant extent. Autumn and winter rests led to lower legume content due to dominance of perennial grasses.

Discussion

These data suggest that favourable changes in botanical composition can be achieved with simple grazing management strategies. These changes depend upon the initial pasture condition. The pasture should contain a reasonable proportion of desirable species. It is important to decide on the ultimate goal for each paddock when implementing grazing strategies; should you try and increase the perennial grass component or the legumes? It can be difficult to do both at once. Autumn and winter rainfall is generally most reliable. Implementing grazing strategies at this time of the year could be expected to give similar results each year. The long rests used in these experiments suggest that a long rotation would produce a similar result. This conclusion is supported for perennial grasses by previous work (1). We anticipate that by implementing practical and cost-effective procedures, the productive life of a pasture can be extended significantly.

Acknowledgements

This research is funded by the Wool Research and Development Corporation.

References

Morley, F.H.W., Bennett, D. and McKinney, G.T. 1969. Aust. J. Exp. Agric. Anim. Husb. 9, 74-84.

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