Which horizon in soil profile is known as top soil ?

Options

A. O-horizon
B. A-horizon
C. B-horizon
D. C-horizon

Answer

To answer the question "Which horizon in the soil profile is known as top soil?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Soil Profile**:
- Soil is composed of different layers, known as horizons. Each horizon has distinct characteristics and functions.

2. **Identifying the Horizons**:
- The soil profile typically includes several horizons:
- **O Horizon**: This is the topmost layer, primarily composed of organic matter like decomposed leaves and other organic materials. However, it does not contain broken down organic particles.
- **A Horizon**: This is the layer directly below the O horizon and is known as the topsoil. It is rich in nutrients and organic matter, as the organic materials from the O horizon have broken down here. This layer is crucial for plant growth.
- **B Horizon (Subsoil)**: Below the A horizon, this layer contains minerals leached from the upper layers and is less fertile than the A horizon.
- **C Horizon**: This layer consists of weathered rock and is the least affected by soil formation processes.

3. **Conclusion**:
- The topsoil is specifically referred to as the **A horizon**. It is characterized by a high concentration of nutrients and humus, making it vital for supporting plant life.

### Final Answer:
The horizon in the soil profile known as top soil is the **A horizon**.

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