Soil
Bedrock to Soil
Soil – a loose mixture of small
mineral fragments and organic
material
Bedrock – layer of rock beneath the soil;
this layer has never been weathered
Sources of Soil
• Parent rock is the rock
that is the source of
the soil.
• The soil made from
granite ( Parent Rock)
will look differently
than the soil made
from limestone.
( Parent Rock)
Sources of Soil
• Residual soil- soil that
remains above the
bedrock from which it
is formed
• Transported soil – soil
that is blown or
washed away(Erosion)
from its parent rock
Sources of Soil
• Humus – very small
particles of decayed
plants and animal
material; also known
as the organic part of
the soil
Soil Layers
• Soil layers are also
known as horizons.
Horizon ‘0’
• Contains fresh or
decaying organic
material (leaves,
plants, animals)
known as Humus.
• Forest soil = Thick
• Desert soil = Thin
Soil Layers
• Leaching –
Rainwater from the
surface travels down
through the horizons;
it dissolves minerals
and nutrients, and
other substances from
the soil above.
Soil and Climate
• TROPICAL
CLIMATES
– CLIMATE - Air is
humid and the land
receives a lot of water
– Leaching occurs
quickly and
constantly, producing
a thin topsoil layer.
Soil and Climate
• DESERT
CLIMATES
– CLIMATE - Very dry
and very little rain
– Water evaporates
quickly, causing the
soil to have large
concentrations of salts,
which can produce
toxic soil (even to
desert plants)
• EX: Death Valley
Soil and Climate
• TEMPERATE
CLIMATES
– CLIMATE - Enough
rain and varying
temperatures
– Thick and fertile soil
develops due to the
abundance of chemical
and mechanical
weathering.
• EX: United States
Soil and climate
• ARCTIC CLIMATES
– CLIMATE - Little
precipitation and
extremely cold
temperatures
– Soil formation occurs
slowly due to cold
temperatures; the
topsoil is extremely
thin and unable to
support most plants.
What do you remember?
• The source of mineral fragments in soil is called
the ______________.
• The organic part of soil is called ___________.
• The soil horizon that contains only humus is
called _______________.
• Soil that remains above the bedrock from
which it is formed is called _____________.
What do you remember? (cont.)
• Describe the topsoil in the desert climates and in
temperate climate.
• What climate in the United States is called the
“breadbasket” for the many crops the region’s
soil supports?
•What do you find at the different horizons or
what is another name?
Horizon A
Horizon B
Horizon C
Horizon R
Answers
• The source of mineral fragments in soil is called
Parent rocks
the ______________.
Humus
• The organic part of soil is called ___________.
• The soil horizon that contains only humus is
Horizon O
called _______________.
• Soil that remains above the bedrock from
Residual Soil
which it is formed is called _____________.
Answers
• Describe the topsoil in the desert climates and in
temperate climate.
Desert – thin and salty
Temperate – thick and fertile
• What climate in the United States is called the
“breadbasket” for the many crops the region’s
soil supports?
Temperate Climate
Answers
• What do you find at the different Horizons?
Horizon A
Horizon B
Horizon C
Horizon R
Topsoil
Subsoil
Partially weathered Rock
Bedrock
Soil and Soil
Conservation
Soil Conservation
• Consists of the various methods by which
humans take care of soil
• http://www.youtube.com/watch?v=nPocNfxvKa
Y&safety_mode=true&persist_safety_mode=1
Review!
• Humus
– Is the part of soil made up of decayed parts of
once-living things
– It is dark and soft
• Soil takes a long time to grow!
– It takes 500-1,000 years to grow 1 inch of soil
– Deep soil takes thousands of years to form
Layers of Soil
• Topsoil
– The top layer
– Made of the smallest
grains
– Richest layer of soil
due to the having the
most humus
• Subsoil
– Layer under topsoil
– Larger grains
– Less humus
• Bedrock
– Solid rock under soil
– Weathering breaks
down rock into soil
– Made of different
minerals
Importance of Soil
• Soil contains the minerals that all living
things need!
What Did We Learn?
• There are many types of soil
• Soils are made from different minerals
• Soils have different colors and different
sized grains
• Soils can hold different amounts of water
• Soils that are best for plants have the right
mixture of minerals and humus
• http://www.harcourtschool.com/activity/dir
t/formation.html
Soil That is Good for Plants
Soil Facts
• Soil is an important resource just like
water, air, trees, and minerals.
• If the same type of crop is grown in soil for
many years on the same land it could harm
the soil.
• Plants use up the nutrients in the soil, then
the soil is too poor for growing more crops.
Why is Soil so Important?
• Minerals and nutrients for plants
• Housing for many organisms (earthworms,
spiders, moles, prairie dogs)
• Storage- Soil stores water
Saving Soil
• Resource: a material found in nature that
living things use
• Conservation: saving resources by using
them carefully
How Can Soils Be Harmed?
• Examples of how soil can be harmed:
1. Cutting down trees
2. Over-farming
3. Erosion- wind and water transport
soil and sediment
Ways to Save the Soil
1. Strip cropping
2. Contour plowing
3. Crop rotation
4. Cover crop
Ways to Save the Soil
1. Strip cropping:
planting strips of thick
grass or clover between
strips of crops
2. Contour plowing:
planting rows of crops
around the sides of hills
(across the slope of a hill)
instead of up and down
Ways to Save the Soil
3. Crop rotation- In order
to prevent nutrient
depletion, crops planted in
certain areas are changed
year to year
4. Cover crop- a crop that is
planted between harvests to
reduce soil erosion and to
replace certain nutrients in
soil
– Ex: Clover and soybeans
What Did We Learn?
• Growing the same type of crop on the same
land for many years removes minerals.
• When people remove plants and trees, soil
may be washed away.
• Farmers conserve soil
The Dustbowl of the 1930s
•
http://www.youtube.com/watch?v=vNKBEbOFrfk&safety_mode=true&persist_safety
_mode=1