Introduction to Soils
Mike Tanti
What soil is made from?
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Soils are complex substances made from a number of
materials and organisms. These include:
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tiny particles of rock of different types
decaying plant material and animal matter
animal life
micro-organisms
water
air.
If these things exist together correctly they form healthy
soil that is essential to good plant growth and
development. Over time, generations of plants have
adapted to grow in different types of soil.
Why soil is important
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Ecology
Soil is a vital component to the ecology of the
planet.
Soil can be seriously affected by changes in
climate, incorrect cultivation and management,
pollution and the removal of the vegetation it
supports.
Once a soil has been damaged or changed, it is
difficult to return it to its original condition.
Why soil is important
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Economy
A fertile soil will produce healthy, plentiful crops.
These crops include trees for timber, decorative
plants, cut flowers and food crops.
In turn, the value of the crops will contribute to
the economy of an area or country.
Why soil is important
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Environment
Soil is essential to the majority of plants.
Soil also provides a home for animals,
insects and other organisms.
How soils help plants grow
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Plants depend on soils for many things
such as nutrients, stability, water, warmth
and air.
If stability, nutrients, warmth, water and
air are not present in soil in sufficient
amounts, a plant will not grow and
develop.
Nutrients
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Soil contains all the essential nutrients plants need for
growth and development.
These nutrients come from the rock particles and organic
matter.
There are 3 major plant nutrients and 10 minor plant
nutrients required by all plants. Specific plants may also
need some other nutrients.
Carbon, hydrogen and oxygen are also classed as
nutrients which are mainly extracted from the
atmosphere.
Nutrients must be dissolved in water before they can be
taken up by plant roots.
Stability
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Plant roots spread
into the soil searching
for water.
The roots firmly
anchor the plant, so it
survives the effects of
weather and damage
from animals.
Roots bind soil
particles together
making the soil more
stable and creating
channels for air and
water.
Water
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Plant roots take up
water from the soil.
Water is needed by
plants for rigidity, as a
transport system and
for processes such as
photosynthesis.
Soil water is stored in
spaces between the
soil particles called
pores.
Warmth
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Soil gets most of its warmth
from the sun (solar energy).
Plant growth and development
occurs as a result of chemical
reactions and these happen
quicker in warm conditions.
Some soils warm up and cool
down quicker than others
depending on their other
properties. For example, a heavy
water-logged soil that contains
little organic matter will cool
down and warm up slowly.
Air
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Air is found in the soil pores
that are not filled with water.
Air in the soil helps plants
take up nutrients, provides
oxygen for underground plant
cells,
gives soil a loose structure to
allow roots to spread
and provides oxygen for the
micro-organisms living in the
soil.
Ideal soil will have both air
and water in the pores.