| 11. | Porosity of subsurface soil is lower than in surface soil due to compaction by gravity.
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| 12. | Strongly developed Planosols with a very silty or sandy surface soil are best left untouched.
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| 13. | Most roots in surface soil are " long ropelike laterals of secondary and tertiary origin ".
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| 14. | Some of the contaminated soil has blown off-site and affected nearby surface soil and surface water.
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| 15. | It is thought that the fine roots help keep the surface soil together and prevent surface erosion.
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| 16. | This iron carbonate then combines with the surface soil and, over time, hardens into a solid mass.
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| 17. | The species is able to exploit high levels of nitrogen in surface soil to achieve local dominance.
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| 18. | Blocky structures are common in subsoil but also occur in surface soils that have a high clay content.
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| 19. | The saw effect took off the surface soil of the island and took down the trees and vegetation.
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| 20. | When environmental conditions are just right, the bacteria can " bloom " and re-contaminate surface soil and grass.
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