Earthworms have a vital role to play in preventing soil erosion by improving water absorption rates, according to results from the Soil and Water Protection (SOWAP) project.

Better infiltration rates are just one of the benefits of a healthy earthworm population, which will become more important as climate change continues to alter rainfall patterns, says Alastair Leake of The Game Conservancy Trust's Allerton Research Trust farm in Leicestershire, where some of the SOWAP work is being carried out.

"Although the total annual rainfall hasn't changed, the pattern of it has," explains Mr Leake.

"We are now getting shorter, sharper bursts of rain, or deluges, which cause more erosion flooding and river pollution.

"For the last two years, August has been the highest rainfall month here at Loddington.

Soil particles in the water are one of the biggest contaminants that have to be dealt with."

Insurance companies are paying out about £3bn a year for flood damage, he adds.

"Much of that is due to water leaving fields.

The solution is to turn the soil into a reservoir, so that the water is there when the crop needs it, rather than a few miles down the road."

SOWAP research suggests that non-inversion tillage can make a big difference to earthworms, as it limits soil disturbance.

"This is particularly relevant for the common earthworm, which makes a permanent, vertical burrow, sometimes to the depth of more than 1m," says Heidi Cunningham of Harper Adams University College.

Where there's a healthy earthworm population, there will be 1000 miles of burrows per acre, she continues.

"Fields with earthworm tunnels absorb water at a rate of 4-10 times that of fields without worm tunnels."

Worms also act as a biological filter, she maintains.

"They line their burrows with mucus which absorbs any pollutants, such as nitrates and pesticides, which are in the water.

They also improve organic matter content."

Ploughing causes two problems for earthworm populations, notes Ms Cunningham.

"Much of the good work done by the worms is destroyed when the soil is inverted.

There are also higher predation rates, as the worms are bought to the surface."

fwarable@rbi.co.uk