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More about soil
Soil types can vary widely on the basis of their chemical, physical and biological properties. Move your cursor over the soil-silt-clay triangle to see how soil varies horizontally and vertically.
Soil is formed from the combined effects of climate, vegetation, soil organisms and time have on rocks and organic materials. Any alteration in one of these components may, therefore, result in changes of the soil.
Soil is a complex system where crucial bio-, chemical- and geo-processes occur. In the top 30 centimetres of one hectare of soil, there are, on average, 25 tonnes of soil organisms: bacteria, fungi, earthworms, springtails, mites, isopods, spiders and coleoptera. Organisms such as snails, mice and earthworms make up from 50 to 75 percent of the total weight of animals in arable soils.
In a layer 1-5 millimetres deep of one hectare, earthworms ingest 18 to 40 tonnes of soil, which is then passed to the surface. The soil fauna and flora recycle organic matter to form humus, which is then combined with mineral material.
Worms also create and maintain the airways within the soil that are essential to plant roots. Soil is necessary for the growth of food crops, fibre and timber, and is an essential component of all terrestrial ecosystems. In contrast with the concerns over the atmosphere and hydrosphere, the need to protect the soil has only recently been appreciated.
Soil is static and thus acts as an enormous receptacle for any type of pollutant that can be mobilised under different triggers (such as acidification) and finally released into the environment. Since the residence time of these substances is far longer in the soil than in air or water, effects often stay hidden for a long time.
Unlike air and water, soil can be owned as personal property, which renders soil conservation and protection policies difficult to enforce and subject to acceptance by landowners and managers.