Download Soils

Soil
Science
Understanding the
Importance of Soil
Objectives
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Explain the importance of soil as a life
supporting layer;
Explain the importance of soil as a medium
for plant growth;
Describe agricultural uses of soil; and
Describe non-agricultural uses of soil.
Life-Supporting Layer
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Soil is a very fragile, limited resource
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It develops very slowly
All life depends on it
Soil interacts with the atmosphere and Earth’s
crust to provide plants and animals with the
resources they need
Life-Supporting Layer
These resources are usually exchanged
through cycles
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Can you think of any natural cycles?
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Water
Carbon
Oxygen
Temperature
Life-Supporting Layer
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Oxygen
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Needed for adequate root growth
Life-Supporting Layer
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Temperature
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Soil absorbs heat from the sun. It
also loses heat to the atmosphere
This cycle provides temperatures
for plant growth and seed
germination
Life-Supporting Layer
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Water
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Utilized for growth of plants
Water is constantly moving to the next stage of the water
cycle
Life-Supporting Layer
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Carbon
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Utilized in the form of organic matter in the soil
Life-Supporting Layer
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Nutrients
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Chemical fertilizers
Organic fertilizers
Plants need soil to grow
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Plants depend on soil to provide four basic needs.
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Anchorage
Water
Oxygen
Nutrients
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Anchorage—soil acts to provide a firm support as
roots grow throughout the soil.
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Water—soil provides nearly all of the water
used by plants. Water is absorbed through the
plants’ roots.
Plants need soil to grow
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Oxygen—nearly all living organisms need
oxygen.
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Plants release oxygen during photosynthesis but
consume oxygen during respiration.
Plant parts above the ground have an ample
supply of oxygen; however, those below the
ground (roots) have less oxygen available.
This increases the need for good soil aeration, the
exchange of soil and atmospheric air in order to
maintain adequate oxygen for plant roots.
Plants need soil to grow
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Nutrients—of the 16 nutrients considered to
be essential for plant growth, 13 are obtained
from the soil.
Root hairs absorb the nutrients dissolved in
soil water.
Uses for Soil- Agriculture
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Agriculture depends on soil to grow food,
fiber, and ornamental plants for human
societies.
Various uses include the following:
Uses for Soil: Agriculture
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Cropland—this is land on which soil is worked and
crops are planted, cared for, and harvested.
Most cropland is devoted to annual crops, such as
corn, soybeans, cotton, vegetables, etc.
Uses for Soil: Agriculture
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Grazing land—this is
land used for grazing
cattle and sheep.
It is often planted to
perennial forage.
Uses for Soil: Agriculture
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Forest—this is land
used for growing trees
which are later
harvested for building
materials, paper, etc.
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This use disturbs soil
the least , but
conservation is still a
major concern
Uses for Soil: Agriculture
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Water structures—ponds and other reservoirs
are constructed out of soil.
Uses for Soil: Non-Ag.
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Humans require soil for many other uses
besides growing plants. Such uses include the
following:
Uses for Soil: Non-Ag.
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Recreation—recreational activities include
playgrounds, sports fields, jogging paths, golf
courses, parks, campgrounds, and many
others.
Uses for Soil: Non-Ag.
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Foundations—
buildings depend on a
solid soil base upon
which to be built to
remain structurally
sound.
Uses for Soil: Non-Ag.
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Construction
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Before building soil must be tested to ensure
sound structure in a building or other structure
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Shrink-swell
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Some soils swell when wet and shrink when dry
Load-bearing Capacity
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Excessive clay or organic matter decreases load-bearing
capacity
Uses for Soil: Non-Ag.
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Homes and other structures
are occasionally built
underground, into hillsides,
or even with soil piled over
them.
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Earth-sheltered buildings
help in lowering heating
and cooling costs.
Prior to shipping of
building materials people
used what they had locally
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Adobe was very common
It is made by mixing 3 parts
sandy soil and 1 part clay
soil then allowed to bake or
dry in the sun.
Uses for Soil: Non-Ag.
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Waste disposal—soil is
often used for the
treatment of human
sanitary wastes.
Soil filters some of the
material, while
microorganisms break
down organic portions
into less dangerous
compounds.
Uses for Soil: Non-Ag.
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Terms to know
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Geotextile
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Plastic mesh used to hold soils in place
Can you think of applications for this?
Shear
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Usually a problem on athletic fields; the tearing of the
soil surface by sideways pressure from shoes