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 protozoa

mesofauna

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