Which one of the following processes during decomposition is correctly described?

Options

A. Catabolism - Last step in the decom- position under fully anaerobic condi- tion
B. Leaching - Water soluble inorganic nutrients rise to the top layers of soil.
C. Fragmentation - Carried out by organism such as earthworm
D. Humification - Leads to the accumu- lation of a dark coloured substance humus which undergoes microbial action at a very fast rate

Explanation

To solve the question regarding which process during decomposition is correctly described, we will break down the concept of decomposition and its associated processes step by step.

### Step-by-Step Solution:

1. **Understanding Decomposition**:
- Decomposition is the process by which complex organic matter is broken down into simpler substances. This process is essential for recycling nutrients in ecosystems.

2. **Role of Decomposers**:
- Decomposers, such as bacteria and fungi, play a crucial role in this process. They feed on dead and decaying organic matter, facilitating the breakdown into simpler forms.

3. **Steps of Decomposition**:
- The decomposition process consists of several steps:
- **Fragmentation**: This is the first step where larger pieces of organic matter are broken down into smaller fragments. This process is typically carried out by detritivores, such as earthworms.
- **Humification**: This step involves the accumulation of humus, a dark-colored organic matter that results from the microbial breakdown of organic material. This process occurs at a slower rate.
- **Leaching**: This refers to the process where water-soluble nutrients are washed away from the soil, often moving deeper into the soil layers, making them unavailable to plants.
- **Catabolism**: This is the breakdown of complex molecules into simpler ones, primarily carried out by bacteria and fungi, often under anaerobic conditions.

4. **Identifying the Correct Description**:
- From the breakdown of the processes:
- Fragmentation is correctly described as the initial breakdown of organic matter by organisms like earthworms.
- Humification is correctly described as the accumulation of humus but is a slower process.
- Leaching is incorrectly described as nutrients rising to the top layer; they actually leach down into deeper soil layers.
- Catabolism is described correctly as the breakdown process but is misidentified in terms of its order in the sequence.

5. **Conclusion**:
- The process that is correctly described in the context of decomposition is **Fragmentation**, as it accurately reflects the role of organisms like earthworms in breaking down complex organic matter into simpler forms.