Download Soil Formation, Weathering, and Classes

Intro to Soils
Objectives

Define terms relating to soil.

Describe factors affecting soil formation.

Describe soil weathering factors.

Describe the procedure for classifying
different portions of land for agricultural
uses.
Soil Terminology

Soil – layer of natural materials on
earth’s surface containing both organic
and inorganic materials and capable of
supporting plant life

Organic matter – dead plant and animal
material in varying stages of decay
Soil Formation

Parent materials – materials underlying
the soil and from which the soil was
formed

5 categories:
– Minerals and rocks
– Glacial deposits
– Loess deposits
– Alluvial and marine deposits
– Organic deposits
Minerals

Solid, inorganic, chemically uniform
substances naturally occurring in the
earth

Common minerals for soil formation
include micas, iron oxides, and silica
Rocks

Three types
– Igneous – formed by the cooling of molten
materials pushed up to the earth’s surface
– Sedimentary – formed by the solidification
of sediment
• Includes rocks that form in layers (river rocks)
– Metamorphic – igneous or sedimentary
rocks that have been reformed because of
heat or pressure
Glacial Deposits

Formed from glaciers scooping up
massive amounts of surface material

Mostly found in midwestern United
States
Loess Deposits


Wind-blown silt
Located in eastern Mississippi Valley
Alluvial and Marine Deposits

Alluvial – Left by moving fresh water

Marine – Left by ancient ocean floors
Organic Deposits

In swampy and marshy areas where
plant life are abundant

Organic substances form in which
plants can grow in
Weathering

The breaking of rocks or soil into
smaller and smaller pieces

Examples include:
–
–
–
–
–
Temperature changes
Water action
Plant roots
Ice expansion
Mechanical grinding
Physical Properties of Soil

Slope – most important factor in
determining the productivity of soil
– Why?

Texture – proportions of sand, silt, and
clay in the soil

Soil drainage – natural ability of soil to
allow water to flow through it

Flood hazard – likelihood that a given
field will receive flood damage
Physical Properties of Soil

Erosion – degree to which soil has
already been damaged

Topsoil / subsoil thickness – depth of
those layers available for plant root
production
Land Capability Classes

8 classes that tell how productive the
land is for agricultural purposes

They are as follows:
– Class I – best land for ag production, safely
cultivated with minimal erosion-control
measures, nearly level, well drained
Land Capability Classes
– Class II – good land for all types of
farming, but may have some limitation
– Class III – moderately good land
• Can be cultivated and farmed regularly, but it
has some important limitations
– Class IV – has severe limitations, but can
be cultivated with careful soil management
Land Capability Classes
– Class V – nearly level land, but has some
soil property making it unsuitable for
cultivation
– Class VI – serious limitations, may be very
rocky or very shallow usable surface soil
– Class VII – severely limiting properties
– Class VIII – one or more extreme
limitations
Objectives

Define terms relating to soil.

Describe factors affecting soil formation.

Describe soil weathering factors.

Describe the procedure for classifying
different portions of land for agricultural
uses.
Intro to ____________
Soil Terminology

_____________ – layer of
____________ materials on earth’s
surface containing both _____________
and inorganic materials and capable of
supporting ________________ life

Organic matter – __________ plant
and animal material in varying stages of
_________________
Soil Formation

_________________ materials –
materials underlying the soil and from
which the soil was ________________

5 categories:
– __________________ and rocks
– ________________ deposits
– ______________ deposits
– ________________ and marine deposits
– Organic _______________
Minerals

Solid, ______________, chemically
uniform substances ________________
occurring in the earth

Common minerals for soil formation
include ___________________,
_________________ oxides, and
____________
______________________

Three types
– ________________ – formed by the cooling of
_________________________ materials pushed
up to the earth’s surface
– _________________ – formed by the solidification
of sediment
• Includes rocks that form in ______________________
(river rocks)
– Metamorphic – igneous or sedimentary rocks that
have been reformed because of ______________
or _____________________
Glacial Deposits

Formed from _______________
scooping up massive amounts of
______________________ material

Mostly found in ___________________
United States
_________________ Deposits

Wind-blown ___________________

Located in _____________________
_____________________ Valley
_________________________ and
Marine Deposits

Alluvial – Left by ______________ fresh
water

Marine – Left by ancient ____________
floors
Organic Deposits

In ______________ and marshy areas
where _______________ life are
abundant

Organic substances form in which
___________________ can grow in
___________________________

The ________________ of rocks or soil
into smaller and smaller ____________

Examples include:
–
–
–
–
–
_______________________ changes
___________________ action
Plant ___________________
Ice expansion
Mechanical ________________________

_________________
Properties of Soil
______________ – most important factor in
determining the productivity of soil
– Why?

_______________ – proportions of sand, silt,
and clay in the soil

Soil ___________________ – natural ability
of soil to allow water to flow through it

_____________ hazard – likelihood that a
given field will receive flood damage
Physical Properties of Soil

Erosion – degree to which soil has
already been ___________________

______________ / subsoil thickness –
depth of those layers available for plant
root production
Land Capability Classes

________ classes that tell how
productive the land is for
________________________ purposes

They are as follows:
– Class I – ________ land for ag production,
safely cultivated with _________________
erosion-control measures, nearly level, well
drained
Land Capability Classes
– Class II – good land for all types of
farming, but _______ have some limitation
– Class III – _________________ good land
• Can be cultivated and farmed regularly, but it
has some important _____________________
– Class IV – has _____________ limitations,
but can be cultivated with careful soil
management
Land Capability Classes
– Class V – nearly level land, but has some
soil property making it ________________
for cultivation
– Class VI – _____________ limitations,
may be very rocky or very shallow usable
surface soil
– Class VII – severely limiting properties
– Class VIII – one or more ______________
limitations