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Classifying Soils. Mr. Lawson. Bellwork. What is different about the soil in AZ and the soil in IL? . Classifying Properties. Soils are classified using the classification system known as Soil Taxonomy. Soils are classified by their properties such as: Soil temperature Soil moisture

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Classifying soils

Classifying Soils

Mr. Lawson



What is different about the soil in AZ and the soil in IL?

Classifying properties

Classifying Properties

Soils are classified using the classification system known as Soil Taxonomy. Soils are classified by their properties such as:

  • Soil temperature

  • Soil moisture

  • Profile characteristics

  • Presence or absence of special horizons

  • Presence or absence of other soil properties

Soil taxonomy

Soil Taxonomy

Order (12 types)- this category is based on the soil forming process. A given order includes soils with properties resulting from similar soil forming processes. This is the most general category.

Suborder (54 types)- soils within an order are divided into suborders based on differences in soil moisture, soil temperature, and soil chemical or textural properties (environmental controls).

Soil taxonomy1

Soil Taxonomy

Great Group (>240)- this category looks at the diagnostic horizons. Soils in the same great group will have the same kind of soil horizon arrangement. There are more than 250 great groups.

Subgroup (>1300)- soils in each great group are divided into one of three types of subgroups (typic, intergrades, characteristics)

Soil taxonomy2

Soil Taxonomy

Family (>8000)- soils in this category are based on properties important for plants or engineering purposes (physical or chemical characteristics)

Series (>19000)- this is the most specific unit of soil classification. It is based on the arrangements and types of horizons. There are more than 19000 soil series in the US.

The 12 soil orders

The 12 Soil Orders

  • 1. Entisol (Sand Hills, Nebraska)

    a. Soils without developed horizons.

    b. light colored

    c. Young soil

    d. Steep slopes

    e. Occur in any climate

    f. 8% of U.S. and world soils

The 12 soil orders1

The 12 Soil Orders

  • 2. Inceptisol (Application Mountains)

    a. Weakly developed soils, but more developed than Entisol

    b. Prone to erosion

    c. Form on top of weathering rock

    d.18% of U.S. soils, 9% of world soils

    e. poorly developed surface horizon

The 12 soil orders2

The 12 Soil Orders

  • 3. Andisol (Pacific Northwest)

    a. formed from volcanic ash.

    b. Dark, organic rich, and fertile soils.

    c. Humid climates.

    d. Found in many locations, but not common.

    e. high in metal (Fe and Al)

    f. young soils

The 12 soil orders3

The 12 Soil Orders

  • 4. Gelisol (Cold regions)

    a. Permafrost (remains below 0 degree C continually)

    b. Form in tundra regions

    c. mineral or organic soil

    d. show cryoturbation (cold disturbance)

The 12 soil orders4

The 12 Soil Orders

  • 5. Histosol (Florida, Michigan, Canada)

    a. Organic soil

    b. Form under wet or cold conditions

    c. Spongy texture

    d. Least common order

    e. dark in color

    f. very lightweight when dry

    g. high water holding capacity

The 12 soil orders5

The 12 Soil Orders

  • 6. Aridisol (Arizona)

    a. In areas dry more than 6 months of the year (desert)

    b. Accumulation of CaCO3 and salts

    c. Productive when irrigated

    d. 2nd most common soil order in the world.

The 12 soil orders6

The 12 Soil Orders

  • 7. Vertisol (Dallas, Texas)

    a. Shrink when dry/ clay swells when wet

    b. More than 30% clay

    c. Fertile

    d. Difficult to cultivate

    e. unstable for engineering

The 12 soil orders7

The 12 Soil Orders

  • 8. Mollisol (Great Plains, Corn Belt)

    a. Dark surface horizons

    b. Usually under grasslands or hardwood forest

    c. Highly fertile, rich in organic matter

    d. Most common order in the U.S.

The 12 soil orders8

The 12 Soil Orders

  • 9. Alfisol (California, Africa, Mediterranean)

    a. Well-developed soils

    b. Fertile (most naturally productive soil)

    c. Second most common order in the U.S.

The 12 soil orders9

The 12 Soil Orders

  • 10. Ultisol (South East U.S., Asia)

    a. Soils occurring in warm, humid climates

    b. Highly leached

    c. Red or dark red in color

    d. Acid soil

    e. require lime to balance acidity and be productive

The 12 soil orders10

The 12 Soil Orders

  • 11. Spodosol (Maine, Florida)

    a. Sandy soils occurring in high rainfall areas

    b. Highly leached

    c. Acid

    d. Usually occur under conifer forests

    e. need fertilization and lime to be productive

The 12 soil orders11

The 12 Soil Orders

  • 12. Oxisol (Hawaii)

    a. Most highly weathered soils

    b. Formed in humid tropical or subtropical climates

    c. Yellow or red in color

    d. Acid

    e. Clay content is high

    f. Low in plant nutrients but some crops are productively grown on it

Ticket out

Ticket Out

  • “To be a successful farmer one must first know the nature of the soil.”

    Xenophon, Oeconomicus, 400 B.C.


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