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Soil
Topic 2052
Anna Blight
What is soil?
• Soil is the product of the rocks from which
it was derived after weathering
• The top layer of the earth’s crust
• Renewable natural resource that supports
life
What does soil do?
• Storehouse for nutrients
• Allows for aeration
• Holds water
• Anchors the plant
Rhizoshpere
• 24” of soil just below the earth’s surface
• Living micro-organisms interact with plant
life
• Urban trees have 80% of their roots in the
top 12” of soil
• What happens to soil at this level is
important for plant health
Soil Quality
• Plants need suitable biotic habitat for
beneficial micro-organisms to live
• Inhibit degradation by
- not allowing compaction from heavy
equipment
- protect soil from run-off or flooding
• Add organic matter to improve quality
Mycorrhizae
• A group of beneficial fungi associated with
roots of plants in healthy soil
• Aid roots in nutrient absorption from soil
Soil Texture
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Percentage of sand, silt and clay
SAND is the largest particle, course texture
SILT is medium textured
CLAY is the smallest particle and is very
fine textured
Soil texture affects:
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Compaction
Ease of tillage
Drainage
Water holding capacity
Nutrient holding capacity
Soil Structure
• Particles group into aggregates
• CLAY helps bind, but too much clay will
form a barrier to drainage
• SAND aids drainage and aeration, but too
much sand causes water to drain too fast
and makes soil dry out
• Excessive tillage destroys structure
Ideal soil composition
• 45% sand, silt and clay mixture
• Pore spaces
25% air and 25% water
• 5% organic matter
Soil and Water
• Depending on soil type, it takes between
200-1000 pounds of water for formation of
1 pound dry matter of plant material
• Amount of water passed through one acre of
corn plants is equal to 16 inches of rain
Soil in nature
• Outdoors, soil is made up of organic matter,
sand, silt and clay
• Different proportions of each will form
different soil textures
• Ideal soil is not too sandy or too much clay
Indoor Soil Mixtures
• Soil less mixtures are usually a mix of peat,
perlite, vermiculite and bark
• Perlite is white and aids in drainage
• Vermiculite is gold - copper color and looks
like an accordion, which makes it useful in
retaining water in the mix
Resources
• http://aged.ces.uga.edu/lessons/course01461.htm
• Integrated Plant Health Management Training Program for
Landscape Maintenance Providers, MSU Nursery and
Landscape Team
• http://hubcap.clemson.edu/~blpprt/bobweb/BOBWEB24.H
TM
• http://ltpwww.gsfc.nasa.gov/globe/index.htm