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20. Trials show grazing can be a sustainable use of rehabilitated mine land in Australia's Bowen Basin
When mining commenced at five of the open-cut coal mines we manage in the Bowen Basin of central Queensland, Australia, the legal requirement was that, after mining, the land was to be returned ‘to purposes connected with grazing’. The rehabilitation of these mines has focused on the establishment of pastures that could be used for grazing once mining had finished. To test the sustainability of grazing as a post-mining land use, trials have been conducted for several years at our Blackwater, Norwich Park and Goonyella mines, with positive results.
Establishment of pastures on post-mining landforms in this region not only provides opportunities for productive land use, but also has a significant benefit in minimising erosion.
However, in recent years, the sustainability of grazing as a post-mining land use in central Queensland has been questioned. Without sound management, non-mined lands in the semi-arid regions of Australia have exhibited significant degradation as a result of grazing.
To test the sustainability of grazing as a post-mining land use, grazing trials have been conducted for several years at our Blackwater, Norwich Park and Goonyella mines. These trials have demonstrated that grazing can be sustained on mined lands at stocking rates comparable to those in the region. Similar results have been achieved using the two different management regimes commonly applied in grazing management.
The trials included assessment of cattle liveweight gain, pasture condition and soil erosion at various stocking rates. The primary aim of the trials was to determine the long-term stocking rate for mine rehabilitation pastures.
Grazing at three stocking rates at Blackwater mine yielded good liveweight gains, better gains than on non-mine pasture nearby in the same season. This led to requests from several neighbours for agistment of cattle in other parts of the mine. At the highest of the stocking rates, the grazing pressure was heavier than desirable as the erosion rates measured after grazing were unacceptable. Cattle are now grazing at about the district average stocking rate on 72 hectares of rehabilitation pasture at the mine.
At Norwich Park mine, cattle are grazing on test areas in a second phase of the trial. The stocking rates applied in the first phase had little impact on the pasture condition, even at the higher stocking rate, even though this was close to the district average. Liveweight gains exceeded those from the adjoining unmined land in the same season. Cattle are now grazing on more than 270 hectares of rehabilitated mine land at the mine.
At Goonyella mine, the cell grazing management method was applied with reasonable liveweight gain, despite the drought conditions that prevailed during the season. A selected group of cattle from the herd have also free-grazed on about 80 hectares of rehabilitation pasture with good liveweight gains.
These trials and the extension of grazing to other areas of rehabilitation on the mine indicate that, with appropriate grazing management, mine lands can be used for cattle grazing.
