Which of the following is used as green manure ?

Options

A. Crotalaria juncea
B. Azolla
C. Hevea braziliensis
D. Azadirachta juncea

Answer

### Step-by-Step Solution:

1. **Understanding Green Manure**:
- Green manure refers to specific plants that are grown and then incorporated into the soil to enhance its fertility. These plants are typically rich in nutrients, particularly nitrogen, which is essential for soil health.

2. **Identifying the Options**:
- The question asks which of the given options is used as green manure. One of the options provided is **Crotalaria juncea**.

3. **Analyzing Crotalaria juncea**:
- Crotalaria juncea is a member of the legume family. Legumes are known for their ability to fix nitrogen in the soil, which is beneficial for enhancing soil fertility.

4. **Benefits of Crotalaria juncea**:
- This plant not only helps in nitrogen fixation but also grows rapidly, making it an effective green manure. It enriches the soil with nutrients, particularly nitrogen and phosphorus.

5. **Conclusion**:
- Based on the information, **Crotalaria juncea** is indeed used as green manure due to its properties of nitrogen fixation and rapid growth. Therefore, it is the correct answer to the question.

### Final Answer:
**Crotalaria juncea** is used as green manure.

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