Soils That Hate Water

At school we're taught that soils absorb water. But what we're not told is that some behave unexpectedly and repel water. This seemingly minor detail can cause major problems, as science writer and broadcaster Richard Hollingham finds out.

Richard meets Dr Stefan Doerr at Swansea University, who investigates the effects of so-called hydrophobic soils. While many normal wettable soils can store large amounts of water - around 30 per cent of their volume - soils that repel water stay dry even when irrigated or when it rains.

In regions that have suffered from a spell of drought, hydrophobic soils can exacerbate flooding, because sudden rainfall often runs straight off the surface of the soil rather than being absorbed. These soils also give farmers in drought-prone countries like Australia, northern Africa and the United States big headaches with irrigation.

Stefan's work suggests that microorganisms and organic compounds could be at the root of the problem.

If his team can figure out how to more accurately predict where and when hydrophobic soils flourish, we're likely to see many benefits to society.