PHYSICAL
PROPERTIES
The specific
nature of certain types of soil
makes some soils more beneficial
for crop growing activities as
opposed to road bed construction.
The physical properties of
certain soils such as sands and
gravels the ability to accept and
transmit liquids. Understanding
the different properties of
specific soils helps to clarify
why some soils are more effective
for sewage treatment as opposed
to agricultural operations.
The main physical
properties of soil are:
Texture: refers
to the relative proportion of
different sizes of particles
which make up the soil. The
distribution of certain particle
sizes affects the pore size and
distribution of the soil, which
is directly linked to the ability
of the soil to accept and
transport liquid (drainage). The
larger the particle sizes the
larger the pores, which generally
means the better the ability of
the soil to drain (coarse
gravels). The smaller the
particle sizes and the greater
the percentage of unified
particles, the smaller the pore
size, which reduces drainage
capabilities of the soil (silts
and clays).
Structure:
refers to the manner in which
soils of different
characteristics are arranged in
the natural environment. This
arrangement has an influence on
the soils ability to accept and
transport liquids. Common
descriptions of structure in
soils include:
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Stratified
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Platy
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Fissured
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Blocky
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Lensed
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Granular
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Friable
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This arrangement
between different types of soils
or "peds" is important
when assessing the physical
properties of specific soils,
especially if the soil is being
transported elsewhere for a
specific purpose (ie. raised
leaching bed).
Consistency: refers
to the degree of adhesion or
bonding of the soil particles.
This bonding characterizes the
"feel" of the soil, as
the adhesive properties of
particular soils will make them
feel "soft","firm,
or medium" and "stiff
or hard". Based on the
consistency of the soil an
estimation of the compressive
strength of the soil mass can be
made.
Clay
Mineralogy: The mineral
content of specific types of clay
soils will have an enormous
impact on how well these soils
behave in saturated (flooded)
conditions. The ability of clay
soils to transport water is
directly proportional to the
shrinking or swelling of clay
minerals. Some clay mineral have
the ability to swell
significantly under moist
conditions thereby closing off
soil pores and making the soil
impermeable. The greater the
swelling feature of these types
of soil, the more
"plasticity" of the
soil is noted.
Colour:
The general colour and colour
patterns found in soil are good
indications of the drainage
abilities of soil. Soil colours
are the result of primary soil
particles, iron and manganese
oxides and organic matter on the
soil particles. When exposed to
oxygen, moisture in lesser or
greater amounts, these primary
soil particles oxidize to create
red, yellowish or brown colours
in the soil. Soils which are
commonly saturated or under
moisture conditions will bleach
the oxidized colour, or the
unoxidized soil particles will
exhibit the traditional grey or
bluish colours.
Soil Profile:
Without a doubt, the single most
important feature of determining
soil properties or soil
conditions is a complete
identification of the soil
profile, or soil stratification.
Soil is rarely consistent to any
great depth. Soil types
transported by wind or water over
time accumulate over parent
materials resulting in sometimes
very distinctive layers. By
excavating a series of bore holes
or test holes in the soil, one
can assess the various types of
soil profiles found, and
determine if the profiles of
interest are suitable for organic
soil conditioning, agriculture
use or waste water treatment and
disposal.
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