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The pasture resource base

A.D. Wilson and R.J. Simpson

Faculty of Agriculture and Forestry, The University of Melbourne, VIC 3052


This paper presents an overview of current pastures (improved, volunteer and native) found throughout the sheep grazing areas of Australia, as a background to the associated papers on their management. Survey information is summarised and general conclusions drawn on the reasons for the actual pasture composition found. Management and research needs are discussed.

Exotic pastures have generally replaced native pastures throughout the high rainfall and crop zones, with a continuing trend towards the development of species and varieties that fit finer climatic, soil and situation niches. However, actual composition and productivity on farms differs widely from theoretically ideal mixtures and varieties. In high rainfall areas, annual volunteer grasses and broadleaf weeds make up higher proportions of the pasture than sown clovers and perennial grasses, and there are significant invasions of weedy perennials of low productivity. Clover content is generally low (eg. 15%) and a significant proportion of pastures contain no clover, despite its contribution to soil fertility and animal production. Also the older varieties of subterranean clover and perennial ryegrass that have poorer winter growth, remain dominant.

The targets for management should be pastures of mixed species that can together provide the best year-long production. However, pastures will always trend away from the ideal mixtures that are sown, because ecological processes favour annuals and a diversity of species, in continuously grazed pastures growing in a variable climate. Continual inputs and management are required to retain composition nearer to desired proportions.

In the crop zone pastures are almost wholly annuals, with a dominance of species of short growing season and low dry season quality, such as Vulpia spp. Legumes may contribute up to 25% of these pastures and composition is greatly influenced by herbicide use. The desired composition is driven more by the demands of cropping than of livestock, but both could benefit from the greater use of perennial species such as lucerne that provide a longer growing season and a higher nitrogen contribution to the soil. Improved establishment techniques and management are needed to accomplish this goal.

In the pastoral zone pastures are now dominated by wiry perennials of low nutritive value and by short lived species. Management should be directed towards increasing the proportion of the more palatable perennials that provide green-leaf of high digestibility in any season of the year.

Pastures also have an important role in protecting land from erosion, regulating water tables and for improving soil structure. Deep rooted perennials provide the best land protection, and in most cases these are congruent with high animal production. High annual legume compositions and high rates of utilisation are not consistent with good land protection.

The role of native species is also explored. These remain dominant in drier regions and are also common in high rainfall regions where there is a higher proportion of summer rainfall. It is concluded that these continue to play a useful role in more marginal habitats, but that they remain of lower potential than exotic species in fertilised and sown situations. The management of these, to increase the proportions of the more valuable year-long green species, is seen to be more important than the selection of new varieties to sow. An exception is the marginal croplands, where there is a role for natives that can be sown to speed regeneration.

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