Exploring Soil Horizons and Their Characteristics

John Greville, a professor at Purdue University, introduces soil profiles and their horizontal and vertical variability. He explains the significance of color in identifying soil horizons and details the six master horizons: A (topsoil), B (subsoil), C (parent material), O (organic), E (leached), and R (regolith). Each horizon has distinct characteristics, such as color and composition, which are crucial for understanding soil formation and classification.

What is the term used to describe the variation in soil color and composition as you dig deeper?

• Surface variability

• Horizontal variability

• Vertical variability

• Lateral variability

Which horizon is typically found at the very top of a soil profile?

• C horizon

• B horizon

• A horizon

• R horizon

What is the main characteristic of the A horizon?

• Composed of rocks

• Rich in minerals

• Dominated by organic matter

• High clay content

Which horizon is known as the subsoil?

• A horizon

• B horizon

• C horizon

• O horizon

What accumulates in the B horizon?

• Organic matter

• Sand

• Clay and minerals

• Rocks

What is the C horizon primarily composed of?

• Leached minerals

• Topsoil

• Parent material

• Organic matter

Which horizon is referred to as the parent material?

• E horizon

• C horizon

• B horizon

• A horizon

What does the O horizon primarily consist of?

• Rocks

• Organic material

• Sand

• Clay

What is the E horizon characterized by?

• Composed of rocks

• High organic content

• Leached and bleached appearance

• Rich in clay

What is the R horizon also known as?

• Regolith

• Topsoil

• Subsoil

• Parent material