Download Soil - Laura Banks

Soil
● Soil is a mixture of
minerals and partially
decomposed organic
matter.
● Soil begins as rock, but is
gradually broken down
through erosion.
● Mechanical erosion is the
physically breaking down
of rock by wind and water.
● Chemical erosion changes
the molecular structure
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● O horizon, which is mostly non-
decomposed plant litter.
● A horizon, contains a lot of organic
matter mixed with some minerals.
● Also called topsoil.
● B horizon is a layer of clay, mostly
made of minerals with little organic
matter.
● The C horizon is parent material,
which is the bedrock from which
the soil was formed.
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Erosion from Water
● Mechanical erosion from rainfall takes four forms,
ranked by severity.
● Splash erosion is a tiny crater caused by the impact of
a single drop of water.
● Sheet erosion is the transportation of loose soil
particles along a flow
of runoff water.
● Rill erosion occurs
when the flowing
water coalesces into
small channels.
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● Gully erosion is the
most severe, caused by
rapidly flowing water
creating deep channels
in the ground.
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Wind Erosion
● In arid regions, wind is
the major cause of
erosion.
Topsoil protected from wind erosion by
native bluestem grass, New Mexico, 1957.
Soil Conservation
● Multiple soil conservation techniques were part of the
New Deal programs implemented by President Franklin
Delano Roosevelt.
● Contour plowing reduces water erosion by planting
crops along the slope of the land rather that straight up
and down.
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● Many important commercial plants are row crops,
meaning they must be grown in spaced rows.
● Strip cropping alternates row crops like corn and cotton
with cover crops like oats that completely cover the soil.
● The cover crops trap any soil that erodes from the row
crops.
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● Terracing converts steeply sloped land into a series of
flattened terraces.
● The stair-like terracing slows the downward runoff of
water, reducing erosion.
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● Rows of trees can serve as
windbreaks, reducing
erosion by wind.
● In response to the Dust
Bowl, the Great Plains
Shelterbelt was built from
1935-1942.
● 220 million trees.
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