Wonderful Soil

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Wonderful Soil
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An astonishing material

• One teaspoon of a cracking clay soil has the
  surface area of a football field
• A shrink/swell clay soil can expand/contract by
  as much as 30 as it wets and dries
• One gram of smectite (shrink/swell clay) has a
  surface area of about 800 m²

Clays are arranged in sheets, with water and
nutrients stored in between and around the sheets
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Biodiversity
Microorganisms - one gram of soil may contain a
thousand species and several millions of
individuals
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Biodiversity
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Major support system for life
Water soil stores it and filters it
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Major support system for life
Carbon soil stores it and releases it
Soil is a bigger store of carbon than vegetation
and the atmosphere
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Soils and greenhouse gases

• Soil cultivation and soil degradation result in
  losses of organic carbon which is released as
  carbon dioxide (CO2)
• Agricultural soils (mainly through the use of
  nitrogen fertilisers) are also significant
  emitters of nitrous oxide (a more potent
  greenhouse gas)
• Improved soil management strategies such as
  conservation cropping and reduced grazing
  pressure can increase the store of soil carbon,
  thereby acting as sinks for atmospheric carbon

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Major support system for life
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Major support system for life
Building on
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Civilisation - history
Without water AND fertile soil, early
civilisations would not have developed
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Civilisation - art culture
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When things go wrong
Civilisations fall
Maya
Indus
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When things go wrong
Loss of valuable top soil through wind erosion
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Despite all this
We know more about the movement of celestial
bodies than about the soil underfoot (circa
1500s)
Leonardo da Vinci
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