A joint Australian-UK study has found that deep soils store up to five times more carbon than previously thought.
The research, conducted by scientists at Murdoch University, shows carbon is stored at depths of up to 40 metres.
The paper's authors say the the findings merit a reassessment of the current measurements used to judge soil carbon stores.
"This finding may have major implications for estimates of global carbon storage and modelling of the potential global impacts of climate change and land-use change on carbon cycles," the paper says.
Professor Snow Barlow, from the National Climate Change Adaptation Facility, says the findings mean planting trees to sequester carbon may become a more profitable option for farmers.
"There may be value in actually putting those back to some form of woody vegetation which could sequester carbon, at the same time giving you those shelter and biodiversity benefits," he said.
"In some places in the landscape, particularly Western Australia, that might give you some salinity benefits as well."