The plant most commonly used as green manure is

Options

A. Dalbergia sissoo
B. Polyalthia
C. Sesbania aculeata
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding Green Manure:**
- Green manure refers to plants that are grown primarily to be plowed back into the soil to improve its fertility. These plants are usually rich in nutrients and help in enhancing soil structure.

2. **Identifying Common Green Manure Plants:**
- Various plants can be used as green manure, but some are more commonly used than others. It is important to know which plants are recognized for this purpose.

3. **Evaluating the Options:**
- The options given are Dalbergia siso, Polyalthea, Sysbania articulata, and "none of these."
- Dalbergia siso (commonly known as sissoo) is primarily used for timber.
- Polyalthea is not typically recognized as a green manure.
- Sysbania articulata is also not widely used as green manure.

4. **Identifying the Correct Answer:**
- The plant that is most commonly used as green manure is **Crotalaria juncea**, also known as **sun hemp**.
- Crotalaria juncea is a tropical plant belonging to the leguminous family (Fabaceae) and is known for its ability to improve soil fertility.

5. **Conclusion:**
- Since none of the provided options (Dalbergia siso, Polyalthea, Sysbania articulata) are correct, the answer to the question is **"none of these."**

**Final Answer:**
The plant most commonly used as green manure is **Crotalaria juncea** (sun hemp), so the correct answer is **none of these**.

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