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The wool production zones of Australia iii. productivity & management of the Rangelands

Max Hams

"Koralta Station", Broken Hill, 2880


The productivity of rangelands in the Broken Hill region is dependent on maintenance of native perennial grasses such as Mitchell grass and edible shrubs including saltbush and bluebush. Carrying capacity varies greatly with seasonal conditions and the plant species present in a paddock. At our property, "Koralta" we average about 6 ha/DSE, but on occasions stocking rates may reach 3 ha/DSE. Soils vary from low fertility sands to very productive black soil in flood plains. The most appropriate land use in the region is often wool production although annual dispersement of aged ewes, wether hoggets and cull ewe hoggets can generate significant income in some years. Rainfall is erratic and so management must be geared to take advantage of rain whenever it falls.

Shrub control and maintenance of a vigorous perennial pasture is the key to good management of rangelands. Woody weed invasion has already reduced production to one-third of potential on five million hectares and threatens an additional twenty million hectares. Many properties with dense shrub cover are not viable. Budda, turpentine, hopbush, punty African boxthorn and cassia are problem species which often reach densities of many thousands per hectare.

Chemical and mechanical methods are being used to eradicate sparsely populated plants to remove source of seed for subsequent colonisation. However, logistics and cost of herbicide application to shrub population exceeding 1000 per hectare are out of proportion to the productivity and value of land.

For effective use of herbicides, more information is need to define the seasonal period when shrubs translocate carbohydrates to roots. Application of chemical at this time would maximise kill with minimum rates.

Blade ploughing, chaining and fire are the main methods used for reclamation of invaded areas. Except for marginally arable areas, the economics of mechanical reclamation are prohibitive. This is due to an inability of desirable perennial grasses and forbs to re-colonise quickly after soil disturbance. Introduced perennial grasses selected for their ability to compete with shrub are needed to enable managers to control rangeland vegetation. The feasibility of using goats and fire either alone or in combination with mechanical and chemical methods is under study.

Grazing systems are also needed to suit the specific needs of desirable plant species. Positive response to deferment of grazing during critical periods in the life cycle of the main species has been documented for range types of low resilience. However, further detailed studies of the life history of both desirable and undesirable (eg. barley grass, low value shrubs) species under various grazing pressures and systems are needed to enable the merits of grazing strategies such as the Savoury and Merrill systems to be exploited on Australian rangelands.

Rabbit control and exclusion of kangaroos are also important components of grazing systems as positive impacts of livestock removal during deferment may be countered by an increase in grazing pressure of native fauna resulting in undesirable increases in low value trees and shrubs.

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