Soils KT#4

A

Mineral horizon formed at or near the soil surface

Ah

Accumulation of soil organic matter (SOM)

Ae

Ae Removal of clay, SOM, iron, or aluminum

Bh

Bh Accumulation of SOM

Bf

Bf Accumulation of iron and/or aluminum

Bss

Presence of slickensides (smooth clay coating caused by stress in high clay soils)

Bv

Vertic horizon caused by turbation (mixing) of material in high clay soils

Bt

Accumulation of clay

Bn

Bn Strong soil structure and sodium accumulation

Bg

Bg Mottling and gleying due to water saturation

Bm

Bm Slight colour or structural changes from the parent material

Cca

Cca Accumulation of Ca and Mg carbonates

Cs

Cs Accumulation of soluble salts

Ck

Ck Presence of original Ca and Mg carbonates

CssCg Mottling and gleying due to water saturation

Css Presence of slickensides

Cg

Cg Mottling and gleying due to water saturation

W

Water layer

Of

Of Composed of fibrous materials of readily recognizable origin

Om

Organic materials in an intermediate (or mesic) stage of decomposition; some have a recognizable form, but the remainder is highly decomposed

Oh

Organic material which is highly decomposed (in a humic state); the origin of the material is unrecognizable

Define soil.

The naturally occurring, unconsolidated, mineral or organic material at the earth's surface that is capable of supporting plant growth.

L

L Leaf litter, readily recognizable

F

F Partially decomposed leaf and twig material (folic material)

H

H Humic material; decomposed organic materials with no original structures

What is the basic unit of soil?

A pedon.

State the general purposes of soil classification. (5)

• to organize the knowledge of soils to be recalled systematically, communicated, and relationships can be seen

• soil management

• creating hypotheses about soil genesis

• soil surveys, teaching soils

• land use strategies

Order

Based on properties of the pedon that reflect the nature of the soil environment and the effects of the dominant, soil-forming processes.

Great group

• Formed by subdividing each order

• based on properties that reflect differences in the strengths of dominant processes, or a major contribution of a process in addition to the dominant one.

  • e.g. in Luvic Gleysols the dominant process is considered to be gleying, but. clay translocation is also a major process.

Subgroup

• Formed by subdividing each great group

• Also differentiated based on the kind and arrangement of horizons that indicate conformity to the central concept of the great group (e.g., Orthic), intergrading toward soils of another order (e.g., Gleyed, Brunisolic), or additional special features within the control section (e.g., Ortstein, Vertic).

Family

• Formed by subdividing subgroups

• Differentiated based on parent material characteristics

  • e.g. particle size, mineralogy, calcareousness, reaction, and depth, and on soil climatic factors

Series

• Formed by subdividing families

• Differentiated based on features of pedon

  • such as horizon characteristics (color, texture, structure, etc.).

Pedon vs. Series

A pedon is a real unit of soil in the landscape; a series is a conceptual class with defined limits based on the generalization of properties of many pedons.

Pedon size.

Lateral dimensions are 1-3.5 m and its depth is 1-2 m

What is the general relationship between soil taxa and the environment?

Soil taxa, especially at higher levels, reflect environmental and genetic factors like climate, vegetation, parent material, and soil-forming processes.

What is the basis for selecting diagnostic criteria at higher taxonomic levels?

Criteria are chosen to reflect environmental conditions and soil-forming (genetic) processes, not just arbitrary property thresholds.

How do environmental relationships change at lower taxonomic levels?

They become more specific or localized

Do all soil orders have clear environmental relationships?

No. Some, like Regosolic and Brunisolic soils, have less clear relationships with environmental factors.

What are the typical environmental conditions for Podzolic soils?

Humid conditions, sandy to loamy parent materials, and forest or heath vegetation.

Why does the Canadian system focus more on surface horizons?

Because 90% of Canada's land is unlikely to be cultivated, making surface horizons more relevant for classification.

What are the major differences between the US vs. Canadian systems?

• In the Canadian system, all horizons up to the surface may be diagnostic; in the U.S. system, subsurface horizons (below plowing depth) are emphasized.

• U.S. system includes a "suborder" category, which the Canadian system does not.