Some of the claims doing the rounds on how much carbon certain packages of cattle country would be capable of sequestering are nothing short of bonkers, a leading Australian soil scientist has warned.
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Producers weighing up taking on a soil carbon project should count on sequestering soil at the lower end of the scale of 0.1 to 2.3 tonnes per hectare per year, Queensland University of Technology's Dr Elaine Mitchell says.
"Obviously, it has to be assessed on a case-by-case basis but we need to put some reasonable boundaries around this question to manage expectations, given what is being claimed," she said.
"The best available information we have for long-term sequestration - that is over 25 years - includes two recent research trials funded by Meat & Livestock Australia, where the sequestration rates are coming out 0.35t/ha and for time-controlled grazing at 0.5t/ha.
"Where we have seen higher rates measured in Australia at the 1.2t/ha mark, it was done over a short time frame - five years, where we'd expect the most gains to be made early.
"And it was on country converted from cropping to pasture. Where you have soils depleted of carbon you will get a higher rate of gain in the initial phase.
"So I don't think we can expect that in the 25-year time frame.
"Rates over 2t/h have been influenced by rainfall, and are typically quoting international studies where systems are vastly different.
"Claims of 8t/ha are just bonkers. That is biophysically impossible."
The bottom line, Dr Mitchell said, was that producers should be conservative in their assumptions when putting together a business case for a soil carbon project because at the moment, that was where the data was sitting.
Dr Mitchell was one of a number of high-calibre soil science speakers at the Wilmot Cattle Company field day near Armidale last week.
Chief grazing officer with carbon project developer Atlas Carbon, Bart Davidson, also addressed the 350 people who attended.
He made the case the potential amount of carbon that could be sequestered actually does not matter - what matters is if it improves an operation and allows for a risk/reward ratio the producer is happy with.
"It's the same as for any other business decision," he said.
"It doesn't need to be a lot of carbon to work financially but if you need to spend a tonne to get a tonne it doesn't work.
"You might get 0.2 to 0.3t/ha, which is pretty achievable, and to do that only costs you the equivalent of 0.05t so it is worth talking about."
No one should be going into a carbon project without knowing what their soils are capable of, Mr Davidson said.
"A carbon project is not a decision, it's a thousand decisions. It's every time you make a call on how you move animals around or what your stocking rates are," he said.
Shan Goodwin
Shan Goodwin steers ACM’s national coverage of the beef industry. Shan has worked as a journalist for 30 years, the majority of that with agricultural publications. She spent many years as The Land’s North Coast reporter and has visited beef properties and stations throughout the country and overseas. She treats all breeds equally. Contact 0427686187. E: s.goodwin@austcommunitymedia.com.au
Shan Goodwin steers ACM’s national coverage of the beef industry. Shan has worked as a journalist for 30 years, the majority of that with agricultural publications. She spent many years as The Land’s North Coast reporter and has visited beef properties and stations throughout the country and overseas. She treats all breeds equally. Contact 0427686187. E: s.goodwin@austcommunitymedia.com.au
