Soil Horizons

The environment under which this soil developed is currently stable with no waterways close by. The farmer even took a photo of the upper part of the soil profile!

**The soil profile of Mr. Jim Shortz’s land in Southeast Colorado**. *Image courtesy of Dr. Paul McDaniel, Soil and Land Resources Division,* *University of Idaho*

Quiz

Question

Question 1: Is this soil rich or poor in terms of fertility?‏

To review this concept click on the links: Soil Genesis and Development Lesson 1.4 - Sedimentary Rocks

Rich

Sedimentary rocks, such as shale, tend to develop into soils which are deep and probably rich in clay content. Thus these soils would be rich in terms of fertility. Unfortunately, Mr. Jim Shortz's soils did not develop from shale.

Poor

Sedimentary rocks, such as sandstone, tend to develop into soils which have poor fertility. They are dominated by quartz which doesn't have a lot of nutrients present in the mineral structure. Sandstone derived soils, however, have excellent drainage because they tend to be sandy.

Looks Good! Sedimentary rocks, such as sandstone, tend to develop into soils which have poor fertility. They are dominated by quartz which doesn't have a lot of nutrients present in the mineral structure. Sandstone derived soils, however, have excellent drainage because they tend to be sandy.

Question

Question 2: Based on the above information, which soil horizons are most likely present at this site?

To review this concept click on the links: Soil Genesis and Development Lesson 4.3 - 4.5

A and C

A and C horizons are found in young soils, between 50 and 500 years of age. The soil in SE Colorado is much older.

C only

All soils have a C horizon, which is considered parent material, or the material from which the soil is formed. From the soil profile photo you should be able to see at least 2 horizons - a dark upper horizon and a lower lighter colored horizon.

A, B with clay accumulation, and C

The soil is between 500 and 5000 years old. During this time period the sorting of sand, silt, and clay has occurred to the extent that physical movement of clay in to the B horizon has occured.

O, A, E, B with clay and iron accumulation, and C

Soils with a tremendous amount of weathering would contain a zone of eluviation known as an E horizon. These soils tend to be between 50,000 and 500,000 years old.

Looks Good! The soil is between 500 and 5000 years old. During this time period the sorting of sand, silt, and clay has occurred to the extent that physical movement of clay in to the B horizon has occured.

Question

Question 3: The 30 year contract is nearing the end. The farmer, Jim Shortz, had applied 100 tons (approximately 3 inches) of biosolids on top of the soil annually over the past 30 years. The organic matter content of this layer is greater than 25%. As compared to the soil adjacent to his farm where no application occurred, which horizon might now be present in Jim’s soil following biosolids application?‏

To review this concept click on the links: Soil Genesis and Development Lesson 4.3

A 'A' Horizon

The A horizon is considered a mineral horizon, but the farmer has added lots of organic matter, not minerals.

An 'O' Horizon

Given the fact that the horizon contains greater than 25% organic matter, this horizon would be considered an O horizon.

An 'E' Horizon

The E horizon is a zone of strong leaching or eluviation. It is a horizon which has experienced a loss. The farmer has added material to the soil.

A 'B' Horizon

Although the B horizon can be considered a zone of accumulation or illuviation, it is a mineral subsurface zone. The farmer has added material to the upper soil.

A 'C' Horizon

The C horizon is unaltered parent material. The farmer has altered the soil via biosolids addition.

Looks Good! Given the fact that the horizon contains greater than 25% organic matter, this horizon would be considered an O horizon.

Question

Question 4: Which other horizon might be measurably or visibly different after 30 years of biosolids application‏?

To review this concept click on the links: Soil Genesis and Development Lesson 4.3

The 'A' Horizon

The A horizon is typically found at the soil surface. Applying biosolids over an A horizon would most likely alter this horizon.

The 'B' Horizon

The B horizon is a mineral subsurface horizon. They are zones of accumulation, called illuviation, because materials are transported downward and accumulate in this horizon.

The 'C' Horizon

The C horizon is unaltered parent material. It is the material from which the soil develops and tends to be found at the bottom of the soil profile.

Looks Good! The A horizon is typically found at the soil surface. Applying biosolids over an A horizon would most likely alter this horizon.

Question

Question 5: If an O horizon couldn’t develop given the climatic conditions of southeastern Colorado, in which horizon will these organic materials?‏

To review this concept click on the links: Soil Genesis and Development Lesson 4.3

A 'C' Horizon

The C horizon is unaltered parent material and is located at the very bottom of the soil profile photo (see the beginning of this exercise). The farmer has not altered this soil horizon via biosolids addition.)

An 'E' Horizon

The E horizon is a zone of strong leaching or eluviation. It is a horizon which has experienced a loss. It tends to be very light in color. However, there actually is no E horizon present in the soil (see the soil profile photo at the beginning of this exercise.)

A 'B' Horizon

Although the B horizon can be considered a zone of accumulation or illuviation, it is a mineral subsurface zone. The farmer has added material and possibly pollutants to the upper soil.

An 'A' Horizon

The A horizon is the surface horizon and thus this would be the zone farmer Jim Shortz would be adding biosolids to. The pollutants in biosolids would end up in this horizon.

Looks Good! The A horizon is the surface horizon and thus this would be the zone farmer Jim Shortz would be adding biosolids to. The pollutants in biosolids would end up in this horizon.