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