Horizon

Definition

A horizon is a distinct layer of soil that has unique physical and chemical properties compared to other layers. These horizons are part of the soil profile and influence plant nutrition and soil health.

5 Must Know Facts For Your Next Test

1. Horizons are identified by letters such as O, A, B, C, and R, each representing different characteristics.
2. The A horizon, also known as topsoil, is rich in organic material and crucial for plant growth.
3. B horizon or subsoil contains minerals leached from the A horizon but has less organic matter.
4. The C horizon consists of weathered parent material from which the upper layers derive.
5. Soil horizons form through processes like leaching, organic matter accumulation, and weathering.

Review Questions

• What are the main differences between the A horizon and B horizon in terms of composition?
• Why is the A horizon particularly important for plant growth?
• How do soil horizons form over time?

Related terms

Soil Profile: A vertical section of soil that shows all its horizons.

Leaching: The process by which soluble substances are washed out of the soil into lower layers.

Organic Matter: Decayed plant and animal residues in the soil which contribute to fertility.