Mr Illes said a layer of soil 2cm deep (0.8 inches) would need to be removed from the whole of the contaminated region.
In the tropics, they take up water from the deep soil and release it as vapor in the air.
Another experiment the team are carrying out involves taking a metre-deep soil sample, which co-researcher Rebecca Rowe describes as "quite unusual".
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It comes from a garden wholesaler, which provides the high quality soil, taken deep beneath the earth's surface -- 10 meters down, in fact.
By the time he came back to Stanford in 1992, Khosla was neck-deep into manipulating soil bacteria to make better drugs.
But Egypt has been building an iron barrier, sunk deep into the sandy soil, to thwart this subterranean traffic.
The permafrost underneath those trees is melting, exposing deep layers of peat soil that has locked away carbon for thousands of years.
"The French are attached to Algerian soil by roots too old and deep to think of tearing them up, " he wrote in 1955.
Modest and good-natured, he had deep roots in our American soil.
The region's hard-packed clay soil welcomes a unique mix of plants with deep-penetrating root systems.
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Here, the deep burnt sienna red of the soil - rust-coloured because of its richness in iron - mingles with thickets of foliage and a sweep of clear sky.
That seed is germinating deep beneath an obscuring layer of thick, black soil.
Deep chewing of plant roots, paired with the repeated soil chipping of hooves, caused dormant seeds to germinate and water to penetrate below the surface.
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This is achieved due to its soil, which sits on a gravelly plateau where the vines have to dig deep to extract the nutrients.
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Homes that are built to exploit gorgeous views yet withstand severe storms and flooding require clever structural and soil engineering but also another key ingredient: elevation on pedestals or pilings sunk deep into bedrock.
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