Gathering soil-carbon data sets up Archers for future

Eric Barker March 11, 2024

Goondiwindi grazier Tom Archer presents at the recent Wilmot Cattle Co. Field Day at Ebor, NSW. Photo: Eric Barker

ONE of Australia’s soil-carbon pioneers says he is hoping a comprehensive dataset being gathered on the grazing operation will help with future environmental market opportunities.

Tom and Antoinette Archer, who own Rexton and Rainmore near Goondiwindi, were part of the first group of producers to be issued large numbers of soil carbon credits last year.

Tom gave an insight into the sheep and cattle grazing operation at the recent Wilmot field day.

The family has had a long interest in improving the landscapes under their management, working with well-known consultancy business RCS, and ultimately signing up to a soil-carbon project in 2016 with the company’s subsidiary Carbon Link.

The Archers have made a series of management changes over the years, introducing legumes, sub-tropical grasses and time-controlled grazing, which has involved a significant increase in paddock numbers and development of water points.

“There has been a fair bit of capital expenditure, a lot of that was early on in the transition,” he said.

Mr Archer began his presentation by running the crowd through a series of photos that showed the changes in landscapes across the two properties.

The photos showed the properties maintaining groundcover in the 2018-19 drought, and clear water running off paddocks while topsoil stayed on the property during and when the drought-breaking rain eventually came.

“We are not exporting our topsoil down the creek,” he said.

It also showed how the management plan had turned paddocks with barely any sign of Mitchell grass into a full body of that pasture and how water that used to sit in melon holes was now being absorbed into the soil.

Early interest in soil carbon

While the time-controlled grazing started on Rexton in the early 2000s, the interest in soil carbon started in 2008.

With the help of Terry McCosker, the Archers took a series of soil samples down to about 10cm using a shovel.

By 2016, the soil-carbon market had become a reality and they decided to take the same samples from similar areas which had shown some increases in carbon levels.

“We now know the top 10cm is the most volatile, but Terry had still calculated about half-a-ton of carbon/ha/year, which was all we had to go by as far as modelling,” Mr Archer said.

“Back then, there were only two carbon service providers and we didn’t have the technology that is available now, which made soil carbon projects a lot more of a punt.”

Looking for another income to smooth out the financial fluctuations of a grazing business, the Archers decided to in 2017 take an initial series of soil core samples which went down to 1.2m.

They then registered a soil-carbon project with the Clean Energy Regulator.

“We also had to demonstrate a change of practice, which was hard on our home property because we had been improving our grazing practices over a long time.

“It was easy on our new property because most of what we did was a change of practice.”

Will high rates of sequestration continue?

Having had the project registered for five years and having dealt with three different carbon-farming methodologies, the Archers had their second round of soil-carbon samples taken in 2021.

Following 18 months of audits, the family was issued 66,000 Australian Carbon Credit Units for their soil-carbon increases.

The project was one of a group of projects to record a high sequestration rate, which has been questioned by a group of scientists, arguing that the result was likely influenced by the high rainfall years that preceded the second test.

The Archers have signed up to the project for 25 years and the project will now be subject to tests every five years.

They have an obligation to keep carbon in the soil and the CER holds 25pc of the credits as a permanence buffer in case of a reversal in carbon sequestration.

Mr Archer said results submitted to the CER were subject to countless audits and he was comfortable with the process.

“I do feel that with the level of testing and the amount of auditing it went through, the results had to be legitimate,” he said.

“We are not sure whether most of that sequestration happened in the year prior to second tests and we are only going to find out about that when do our next tests in five years.

“Will the high sequestration rate continue? We are not sure and we are not budgeting for it. But I guess we are going to be one of the first to out.”

Gathering more soil carbon data

Since signing up to the project, the Archers have also started hosting a Queensland University of Technology study, which is using flux towers to detect fluxes of carbon in and out of the soil.

“The flux towers are sending data back to Brisbane regularly; they have also done some 1.2m core samples near the site and Carbon Link have a couple of core samples around there as well,” Mr Archer said.

“I think that is really interesting because we have independent data from both the university and the soil-carbon industry.”

Mr Archer said he was hoping the data they were gathering would help the business capture opportunities with looming biodiversity markets.

“If we end up in an environment where we are being paid for good practices, we might have a shocking drought that lasts a long time, but we do a good job of managing it – then I think the biodiversity markets can help in this instance,” he said.

“I think the soil-carbon data we have built over many years could be a big part of a future biodiversity business.”

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