Exploiting the biological goldmine in the soil under our feet

The soil under your feet isn't simply dirt; it is a biological goldmine that could also help to slow global warming. It locks up huge amounts of carbon, and could be used to take the important greenhouse gas, carbon dioxide, out of the atmosphere.

The remarkable ability of soil to lock up carbon was described yesterday at the British Association by Prof David Powlson, of the Rothamstead Research Centre, who said that the soil currently traps twice the amount of carbon as is found in the atmosphere.

"Soil is a huge pool of carbon," he said. "With careful management it is possible to manage that pool to remove carbon from the atmosphere."

Carbon reserves in the soil, mainly put there by plants, actually decline with intensive agriculture. "We have more scope in agriculture to put some carbon back" by minor changes in practice, he said, such as widening field margins slightly and the careful use of fallowing. The soil holds much more carbon than the plants growing in it, but levels in the soil actually rise when the plants are in place.

The use of soil for "carbon sequestration" could have a major impact, he stated. Such was the potential that it could allow most EU countries to meet quite easily the tough carbon dioxide output limits set by the Kyoto Agreement. This called for output levels from industry, transport and heating to be held at 8 per cent above 1990 levels. "We are not talking trivial numbers here," he said.

Prof Mark Bailey, of the UK Centre for Ecology and Hydrology at Oxford, is also looking at carbon sequestration, but is using a different approach, identifying the many soil microbes that are good at locking up carbon.

"Micro-organisms represent a huge genetic resource in soils," he said. A single gram of soil held as many as 10,000 separate bacterial species and there was as much or more biodiversity in the soil as in the rainforest in terms of species.

He advocates the "genetic mining of the soil" as a way to identify novel micro-organisms and useful genes.

These soil organisms could also play their part in controlling global warming, he said, providing that those good at holding carbon could be identified.

Bailey is using tagged carbon to follow the element's route from plants into the soil and on to the bacteria. High levels in any species would identify it as a good carbon sequesterer.