Soil Forming Processes | Soil Genesis and Development, Scenario 3 - Soils and Salts

Even though we can’t always see differences among horizons, there are differences present that are measurable in other ways. These differences are present because of four principal processes involved in forming soils: Additions, losses, transformations, and translocations. (see Principles Lesson 4.2 - Soil Profile Development)

Use these terms to answer the following questions.

Quiz

Question

Question 9: The A horizon is darkened by the accumulation of organic matter from dead plants. This is an example of which process?

additions

Organic matter from plants has been added to the horizon, darkening it.

losses

While clay has probably been lost from the A horizon, that process would not darken it.

transformations

The original plant material has been transformed into humus.

translocations

Nothing has been moved from any other horizon into the A.

both additions and transformations

Plant material has been added to the A horizon and been transformed into humus.

both additions and translocations

Plant material has been added to the A horizon, but no material has been translocated into the A.

Looks Good! Plant material has been added to the A horizon and been transformed into humus.

Quiz

Question

Question 10: The B horizon has more clay than either the A above or the C below. Which process is responsible for this observation‏?

additions

While the B horizon has more clay than any other horizon, that clay has not been added from another location.

losses

Clay has been gained by, not lost from, the B horizon.

transformations

In some soils clay can form in place from other minerals.

translocations

Clay is commonly moved downward in a soil as water leaches over time.

both transformations and translocations

The clay accumulation in the B horizon probably occurred both because of formation in place from other minerals (transformation) and downward movement with leaching water (translocation).

Looks Good! The clay accumulation in the B horizon probably occurred both because of formation in place from other minerals (transformation) and downward movement with leaching water (translocation).

Quiz

Question

Question 11: The C horizon is often considered to be the “stuff” from which the soil has formed. If we have a location on a hill slope where a horizonated soil has developed, and a torrential rainstorm occurs which strips off the A and B, leaving only the C behind, what is the process responsible for starting soil formation to begin again‏?

additions

Stripping off the A and B horizons is not a "gain" for the soil.

losses

The A and B horizons are completely lost from this soil, forcing it to begin their formation again.

transformations

No soil material is changed in losing the A and B horizons.

translocations

The A and B horizons are completely lost from this location, not simply moved elsewhere in the soil profile.

both losses and transformations

Soil material is lost from the profile but nothing is changed without movement.

Looks Good! The A and B horizons are completely lost from this soil, forcing it to begin their formation again.

You may have noticed that some or most of the translocations, additions, and losses that affect these soils are related to the soil-forming factor topography. For example, the accumulation of salts in soil 3 (seen in the white crust at its surface) occurs mainly because this soil is low on the landscape and is affected by very salty subsurface water (seen at the bottom of the photo). So salt accumulates by translocation from below. On the other hand, soil 1 has probably been subject to some erosion (a loss of the A horizon) because of its slightly higher location on the landscape and its slope.

If you’d like a simplified overall look at soil formation, go to this soil animation by Wiley Publishers. It details how Salmo soil may have been developed.