INTRO TO SOILS – CH 2
Soil Origin and Development
THE SOIL BODY
•
Pedon – smallest body which can be
called a soil
Three-dimensional
• Typically extends down to depth of plant
root
•
THE SOIL BODY
•
Polypedon – two or more contiguous
pedons
• Form a Soil Series
• Soil Series are the lowest official
category in the soil taxonomy
THE SOIL BODY
•
•
Weathering of rocks and minerals
forms pedons
Two types of weathering:
Physical weathering
2. Chemical weathering
Eventually, a layer of young soil develops
1.
THE SOIL BODY
•
Three types of rock:
1.
2.
3.
Igneous
Sedimentary
Metamorphic
THE SOIL BODY
•
Five (5) Soil Forming Factors
1.
2.
3.
4.
5.
Parent Material
Climate
Living Organisms (plant and animal)
Topography
Time
THE SOIL PROFILE
•
•
Soils change in response to their
environment
Four processes of change:
1.
2.
3.
4.
Additions
Losses
Translocations
Transformations
THE SOIL PROFILE
•
As a soil ages these changes lead to
formation of horizontal layers known as:
• Soil Horizons
These horizons may be exposed when
digging into the soil revealing the:
• Soil Profile
THE SOIL PROFILE
•
Master Horizons:
•
A, B, C
O, A, E, B, C, R
Coded layers of horizon with distinct
characteristics
Not all horizons will always be present!
•
THE SOIL PROFILE
•
Subdivisions and Suffixes may further
define the master horizons
•
e.g. AB, Ap, Bt, Bky
See Appendix 3 for suffix explanations