AS AUSTRALIA’S carbon industry looks for ways to generate more credits, soil carbon projects on agricultural land have been touted as the next frontier.
The idea is to change land management techniques and ultimately build carbon in the soil. For every tonne of carbon dioxide stored in the soil, an Australian Carbon Credit Unit is awarded.
But the industry is young and few long-term scientific studies on the soil’s ability to store carbon – leaving plenty of questions about the burgeoning industry. One of the big questions has been the impact climate change could have soil carbon levels.
The subject was raised by Dr Susan Orgill from the NSW Department of Primary Industries at the Ebor Beef forum in Armidale last month. Most of her work has been in southern NSW.
Dr Orgill said one of the main questions she had been asked was if soil carbon could keep building during drought. She said the best time to build soil carbon was from a low base.
“We found a general increase in soil organic carbon, with seasonal fluctuations,” she said.
“But with our study in southern NSW, which went over the millennium drought, we noticed an increase in soil organic carbon stocks. It might not have been as much as a higher rainfall scenario, but it still increased.
“Good management is the fundamental driver of increasing soil carbon – maintaining good ground cover protection, managing grazing pressure and maintain plant nutrition.”
With a team of scientists, Dr Orgill has been looking at three elements of Australia’s soil carbon:
- Has soil carbon been declining in Australian soils?
- Can Australia sequester carbon in the soil, while continuing to feed the nation?
- Will climate change result in a loss of soil carbon?
The paper found increasing soil carbon was a major part of increasing agricultural productivity.
“It is often soil organic matter that is driving the processes that support agricultural production and enhance soil condition,” the paper said.
“For example, increasing soil organic matter enhances the physical condition of the soil and plays a pivotal role in nutrient cycling.”
While there was a direct correlation between soil carbon and productivity, the paper also noted there had been an estimated 70 percent decline in soil organic carbon (SOC) levels since converting native vegetation to agricultural land use.
“The decline in SOC from agricultural soil has been considerable in Australia, largely due to overgrazing, cultivation and continuous cropping in a dry climate on often highly weathered soils,” the paper said.
“However, the initial sharp decline in SOC has been partially reversed by improved land management practices such as crop rotations, nutrient application, inclusion of pasture phases in cropping rotations, erosion control and conservation farming practices.”
Dr Orgill told the Ebor Beef forum producers should be considering the cycle of carbon in making management decisions.
“If there is one thing producers should think about when trying to improve management practices, it is the way carbon cycles around an ecosystem,” she said.
“That flow of carbon has a big impact on productivity.”
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