wonderful soil. an astonishing material one teaspoon of a cracking clay soil has the surface area...
TRANSCRIPT
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
Biodiversity
Microorganisms- one gram of soil may contain a thousand species and
several millions of individuals
bacteria
algae
Major support system for life
Carbon – soil stores it and releases it
Soil is a bigger store of carbon than vegetation and the atmosphere
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
Major support system for life
Plants – soil anchors, waters, and provides nutrients
Soil makes food & fibre production possible
Despite all this …
“We know more about the movement of celestial bodies than about the soil underfoot” (circa 1500s)
Leonardo da Vinci