While this may appear to be a very
basic question it is in actuality a very complex topic.
Traditional soils have
five basic
components:
- Air
- Water
- Mineral Particles
- Organic Matter
- Biology
Air:
Soil air refers to the gaseous phase of
soil which is neither liquid nor solid. It is estimated
that 25% of any given soil is composed of air that is a
gaseous medium.
Water:
Soil Water or Soil Solution is the liquid
phase of the soil. Soil water contains dissolved salts
and chemicals (in the form of ions) that are
free-floating and not attached to any solid particles
(mineral surfaces). Water also comprises an estimated
25% of any given soil sample.
Mineral Particles:
The mineral part of soil is
composed of varying amounts of sand, silt, and clay. On
the whole these particles are not derived from materials
that were once living, meaning that the minerals are
inorganic. The characteristics of mineral particles
greatly influence soil behavior and management needs.
Sand: The soil component sand is mainly
small rock fragments and hard minerals such as quartz.
It contains few plant nutrients and soils high in sand
can be particularly arid due to high drainage low
nutrient ratios.
Of the three types of soil
particles, sand is the largest in size and provides the
following benefits if used as a soil component in
moderate amounts:
Improves drainage, aeration,
and tilling quality.
Silt: Silt consists
of ground up sand and rock minerals. Silt like sand
contains few nutrients, but it can have nutrients
clinging to its surface.
Silt is between sand
and clay in terms of size.
Clay: Clays
are aluminum-silicate minerals that also have varying
amounts of nutrients important to plants such as
potassium, calcium, magnesium, iron, etc. A good part of
a soil's native fertility can come from its clay
portion.
Clay particles are the smallest of the
three soil mineral components and they have a negative
charge which makes them attract all positive charged
plant nutrients. This helps trace elements stay in the
soil rather than being constantly leached away.
Too much clay can result in harder tilling,
compaction (Lack of air) & poor drainage.
Organic Matter:
Organic matter in the soil
includes plant and animal residues at various stages of
decomposition. There are also the cells and tissues of
soil organisms and substances synthesised by plant roots
and soil microorganisms. It is estimated that organic
matter makes up about 5% of most common soils. Despite
this small proportion, organic matter has a remarkable
effects on soil behavior and crop yields. Organic matter
in the soil is frequently in the form of humus,
partially decomposed organic matter that has become dark
and crumbly and continues decomposing at a slow rate.
Biology:
While not actually a component of soil
in the traditional sense, that is, mineral based there
is a huge living component of soil. This includes the
microorganisms in the soil, the earth worms and the
myriad of other living things which help process organic
and inorganic matter into soil. If we are to look at
soil as a Gestalt then we must include the soil biology.
Here is a good link explaining what soil is
which can be used for further reading if desired:
Four Major Components of Soil
If anyone finds any broken links in the FAQ then
please do not hesitate to PM the author and get them to
update or remove the link/links.
Peace...The
Penguin.