C Horizon

Definition

The C horizon is the layer of soil that lies beneath the A and B horizons, consisting primarily of weathered rock and unconsolidated material. This horizon plays a crucial role in the soil profile as it provides the parent material from which the upper layers develop, influencing both the physical and chemical properties of the soil above it.

5 Must Know Facts For Your Next Test

1. The C horizon typically contains larger rock fragments and less organic material compared to the upper soil horizons.
2. This layer serves as a reservoir for nutrients and minerals that can leach into the upper layers during rainfall or irrigation.
3. The depth of the C horizon can vary significantly depending on local geology and landscape, ranging from a few centimeters to several meters.
4. Unlike the A and B horizons, which are biologically active and rich in organic matter, the C horizon is largely inert and slow to change over time.
5. In many cases, the characteristics of the C horizon determine the drainage properties and nutrient availability of the entire soil profile.

Review Questions

• How does the composition of the C horizon influence the development of the A and B horizons?
  • The C horizon is primarily made up of weathered rock and unconsolidated materials that provide essential minerals and nutrients for the A and B horizons above it. As water percolates through the soil, it can carry nutrients from the C horizon upward into the A horizon, where plant roots can access them. Additionally, the physical properties of the C horizon, such as texture and drainage capacity, directly affect how moisture moves through the entire soil profile, impacting plant growth.
• Discuss the role of weathering in forming the C horizon and its importance in soil health.
  • Weathering is vital for forming the C horizon as it breaks down bedrock into smaller particles that become part of this layer. The process contributes to creating a diverse range of minerals that serve as building blocks for soil fertility. Healthy soil relies on a well-developed C horizon because it provides essential nutrients that support plant life. Without weathering processes, soils would lack diversity in mineral content, leading to poor fertility and reduced agricultural productivity.
• Evaluate how changes in land use might impact the characteristics of the C horizon and consequently affect soil profiles.
  • Changes in land use, such as deforestation or urbanization, can significantly alter the characteristics of the C horizon. For instance, increased erosion may expose more of this layer to weathering processes or compact it due to heavy machinery use. As a result, nutrient availability can decline, affecting not just the C horizon but also how well plants can grow in the A and B horizons. Evaluating these impacts is crucial for sustainable land management practices, which aim to maintain healthy soils for future agricultural productivity.

Related terms

Soil Profile: A vertical cross-section of the soil that reveals its different layers or horizons, including the A, B, C horizons and sometimes R horizon beneath.

Parent Material:

The underlying geological material (rock or sediment) from which soil horizons form through processes like weathering.

Weathering:

The process of breaking down rocks into smaller particles through physical, chemical, and biological mechanisms, essential for soil formation.