ENCOURAGING results from a cattle grazing trial run by the New South Wales Department of Primary Industries (DPI) continue to showcase Rio Tinto’s rehabilitation efforts at its Hunter Valley mines. The four-year project is investigating the effects of grazing on rehabilitated mine land and whether it can sustainably support productive grazing livestock.
At a final weighing on June 1 it was confirmed that steers reared on land rehabilitated by Rio Tinto were 100kg heavier on average than cattle grazed on unmined farm land.
Both groups started on a level playing ground in terms of lineage and weight. In the trial’s second stage, stocking rates on the rehabilitated land were increased above the unmined land to take advantage of excess feed that DPI researchers had observed during grazing in the first stage.
The steers were run on rehabilitated paddocks at the Hunter Valley Operations mine site near Singleton and an adjoining control property as part of the Upper Hunter Mining Dialogue Grazing Study.
Rio Tinto manager environment and community Andrew Speechly said, “The weighing confirmed that cattle on rehabilitated paddocks are outperforming those on unmined paddocks and this time despite 50% higher stocking rates on rehabilitated paddocks.
“The results have been consistently promising and are an indicator that Rio Tinto’s rehabilitation work has paid off. From the data we are collecting it is clear that when done well rehabilitated mine land provides a commercially sustainable option for grazing.
“We continue to draw on the agriculture sector’s expertise to improve our rehabilitation performance.”
The project is managed by the NSW DPI in collaboration with Upper Hunter Mining Dialogue’s joint working group on Land Management, comprising representatives from local grazing and community groups, government and mining companies.
DPI technical specialist pasture production Neil Griffiths said, “Greater available pasture biomass on the rehabilitated pasture can largely explain the weight gain advantage.
‘The final results for the second group showed the steers on the rehabilitated site had an average weight of 480kg/head and 4.3mm fat, while on the analogue site steers weighed 381kg/head and 2.4mm fat.
“This was consistent with the first group, where steers grazing the rehabilitated mine land were on average 153kg/head heavier, and worth $450 more than their mates grazing the nearby native pasture, which was similar to original pasture on the mine site.”