Soil Profile Terminology Quiz

Soil Profile Components

• O-horizon: Rich in organic matter, typically includes layers of leaves, pine needles, twigs, and decomposed humus.
• A-horizon (Topsoil): The uppermost mineral layer, known for its darker color due to high levels of humified organic matter.
• B-horizon: Characterized by leached material accumulation, including soluble materials and minerals like clay, iron, or aluminum.
• C-horizon: Composed of weathered rock that has minimal influence from soil-forming processes.
• D-horizon (Bedrock): The deepest layer, consisting of unweathered mineral matter or different mineral complexes that form the foundation of soil layers.

Soil Features

• Humus: Organic component created from the decomposition of plant material, essential for soil health and fertility.
• Topsoil: The uppermost layer, typically 2-8 inches deep, crucial for plant growth due to its highest organic matter content.
• Subsoil: Located beneath the topsoil, a mix of fine particles lacking organic matter and humus, important for water and nutrient retention.
• Weathered rock fragments: The lowest zone in soil profiles, primarily made up of loose rock materials that may serve as a substrate for soil development.
• Bedrock: Solid, intact rock located below regolith; serves as the foundational layer from which soil layers develop.