Notes: Soil Formation and Composition
Soil Formation
Soil – The loose, weathered material on Earth’s surface in which
plants can ________.
How is soil formed?
Soil is formed as rock is broken down by _______________ and
mixes with other materials on the surface.
Bedrock – The __________ layer of rock beneath the soil. It
gradually weathers into soil whenever it is exposed.
Soil Composition and Texture
Soil is a mixture of ___________ particles, minerals, decayed
organic material, air, and water.
Humus – Dark colored the decayed organic material in _______;
helps create ______________ in soil for air and water; rich in
elements that plants need
Loam – soil made up of about equal __________ of clay, sand,
and silt; ideal for most plants
Soil Particle Size
Soil Layers
Soil Horizons
Soil horizon – layer of soil that __________ in color and texture
from layers above or below it.
Topsoil – Mixture of humus, _________ and other minerals that
forms the crumbly, topmost layer of soil; the _______ horizon
Subsoil – The layers of soil beneath the ___________ that
contains mostly clay and other minerals; the _______ horizon
Soil
1. Soil is a combination of _____________ and
_________________.
Notes: Soil Formation and Composition
2. ____________ = decayed plant and animal material found in
soil. Soil that contains 20-30% humus is considered a rich soil
for plant growth.
Soil development
Soil layers- The soil profile
___________ or ___________ = the top layer of soil that
contains more humus than the layers below.
___________ or ___________ = consists of clays and dissolved
minerals that have been washed down from above. Contains
less humus.
___________ = consists of weathered rock fragments, usually
from the parent rock below.
___________ = the layer of rock beneath the soil. Frequently
the parent rock of the soil above.
Georgia’s soil
Southern Forest soil – form in _______ and _________ climate;
low in humus.
Forming Humus
Litter – The loose layer of dead plant leaves and stems on the
surface of ________.
Decomposers – Soil organisms that ___________ down the
remains of dead plants and organisms and digest them.
Importance of Living organisms in
Soil
Some soil organisms, like earthworms, _________ the soil and
make spaces in it for _______ and water.
Other soil organisms make humus, which makes soil
__________.
Notes: Soil Formation and Composition
Soil Conservation
Soil is one of Earth’s most _____________ resources because
everything that lives on the land depends directly or indirectly
on soil.
Fertile soil is valuable because there is a ____________ supply.
Less than 1/8th of the land on Earth has soils well suited for
farming.
Soil Damage and Loss
Soil can become exhausted, or ________ its fertility.
Soil can also become lost to ____________ by water and wind.
 __________ erosion can occur wherever soil is not
protected by plant cover.
 ___________ erosion caused the Great Dust Bowl!!
Sod – The thick mass of tough roots at the surface of soil keep
the soil in place and hold onto moisture.
The Dust Bowl – Loss of Topsoil
In the 1930s plowing removed the grass form the Great Plains
and _____________ the soil. In times of drought, the topsoil
quickly dried out, turned to dust, and blew away.
This event helped people appreciate the value of soil.
How to help in Soil Conservation?
Soil Conservation is the management of _________ to prevent
its destruction.
Three ways that soil can be conserved include contour plowing,
conservation plowing, and crop rotation.
Contour Plowing
Contour plowing is the practice of _____________ fields along
the contours of a slope.
This helps slow the ____________of excess rainfall and
prevents it from washing the soil away.
Conservation Plowing
Conservation Plowing disturbs the ________and its plant cover
as little as possible.
Dead weeds and stalks of the previous year’s _________ are left
in the ground to help return soil nutrients.
Crop Rotation
Farmers ____________ different crops each year.
Different type of crops ______________ different types of
nutrients from soil.