Download Soils overview

Wonderful Soil
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
Biodiversity
fungi
mesofauna
protozoa
Major support system for life
Water – soil stores it and filters it
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
Major support system for life
Building – on
Building – with
Civilisation - history
Without water AND fertile soil, early civilisations would not
have developed
Civilisation - art & culture
When things go wrong
Civilisations fall
Maya
Indus
When things go wrong
Loss of
valuable top
soil through
wind erosion
Despite all this …
“We know
more about
the movement
of celestial
bodies than
about the soil
underfoot”
(circa 1500s)
Leonardo da Vinci