PROVING the agricultural and mining industries can work harmoniously together, a grazing trial conducted on unmined land has shown encouraging results.
Stage two of the scientific trials, aimed at comparing livestock production performance of rehabilitated land with that of unmined land at Acland Pastoral Company, has concluded.
The trial, which includes livestock, pasture and soil monitoring , focused on measuring the productivity, economic viability and sustainability of beef production from previously mined land.
Results show that, on average, performance from cattle grazing the rehabilitated pastures was comparable or exceeded the performance of the control (unmined) site with an average gain of 0.7kg/day and producing 103kg of beef/ha.
The trials, which commenced in November 2013, were conducted with the assistance of industry experts including pasture agronomists, soil scientists, a veterinarian and an independent statistician, and were overseen by Armidale-based independent agricultural consultants Outcross Agri Services.
Tom Newsome from Outcross Agri-Services says the cattle trial was a unique project compared to the usual mining industry approach to land rehabilitation.
“Traditionally the mining industry focuses on an environmental outcome and not a commercial outcome as well,” he said.
“This project focused on rehabilitating the land so it can be used for viable and sustainable cattle production into the future.”
Four new sites were selected to be used in stage 2 of the grazing trial. Three of the sites were previously mined and subsequently rehabilitated and sown to sub-tropical pastures; each representing a different age of rehabilitation (2007, 2010, and 2012 respectively) and pasture establishment.
An unmined paddock, sown to sub-tropical pastures in the same year as the youngest rehabilitated (2012), was used as the control.
Acland Pastoral Company (APC) Manager Ben Muirhead said the cattle selected and monitored for Stage 2 of the trial (90 steers, 90 heifers) were selected on the basis that they were the same breed and bloodline; were a single year drop and were sourced from a single vendor.
“This ensures we are comparing the same breed, genetics and age for all beasts in the study.” He said.
The cattle were grazed on the trial sites over three separate grazing periods to reflect a commercial rotational grazing management system and to collect data across a range of seasons.
“Between grazing periods, all trial cattle ran as a cohort and were grazed on unmined sub-tropical pastures, planted in 2012.”
Mr Muirhead said Stage two of the cattle trials had also seen some refinements in the program from Stage one.
“We broadened our testing program in Stage two to include both the soil and pasture performance as well – to gain a more in-depth understanding of the rehabilitated areas,” he said.
“We wanted to investigate the structure of rehabilitated soils compared to unmined soils.”
University of Southern Queensland’s Dr John McLean Bennett said it is still early days yet in terms of the soil work, as that will continue for another three seasons.
“Properties and profile characteristics of the control site and 18 nearby grazed soils (benchmark sites) were also compared to identify how representative the control site was of surrounding grazed land,” Dr Bennett said.
“To rehabilitate land, stockpiled soil is spread to a target depth of 30 cm onto deep ripped and profiled inter-burden (mine spoil) material before being sown to pasture species.
“Once established and considered stable, the rehabilitated land is used for cattle grazing. So far we have observed a comparable range of rooting depths in the unmined soils to rehabilitated soils.
“This suggests that the inter-burden (mine spoil) is capable of supporting the pasture.
“There was little difference in the measured soil chemical properties between the control and rehabilitated sites with regard to benefits or constraints to pasture production. On average, none of the tested rehabilitated sites and depths would be considered sodic or saline.”
Pasture and land management specialists Ecorich Grazing conducted the pasture work measuring pasture growth, quality and quantity on offer at each grazing by cattle.
Col Paton at EcoRich Grazing, said the pasture data collected indicates that the rehabilitated pastures are as productive, and of a similar quality, as the control (unmined) pasture.
“Interestingly though results displayed from the rehabilitated pasture sown in 2010/11 indicate that the site is more productive than other sites,” he said.
New Hope established the Acland Pastoral Company in 2006, as a farming, grazing and land management enterprise based at the New Acland mine.
The APC manages 10,000 hectares of land, and also grows both fodder and grain crops in suitable areas.