An organism used as a biofertilizer for raising soyabean crop is

Options

A. Azotobacter
B. Azospirillum
C. Rhizobium
D. Nostoc

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for an organism that acts as a biofertilizer specifically for raising soybean crops.

2. **Identifying the Options**: The options provided are:
- a) Azotobacter
- b) Azospirillum
- c) Rhizobium
- d) Nostoc

3. **Analyzing Each Option**:
- **Azotobacter**: This is a free-living nitrogen-fixing bacterium, but it is not specifically associated with leguminous plants like soybeans.
- **Azospirillum**: This bacterium is also a nitrogen fixer and is known to associate with various grasses, but not specifically with legumes.
- **Rhizobium**: This is a well-known nitrogen-fixing bacterium that forms symbiotic relationships with leguminous plants, including soybeans. It resides in root nodules and helps in fixing atmospheric nitrogen, making it available for the plant.
- **Nostoc**: This is a cyanobacterium that can fix nitrogen but is not specifically associated with soybean crops.

4. **Conclusion**: Among the options, Rhizobium is the most suitable organism that acts as a biofertilizer for soybean crops due to its ability to fix nitrogen in association with leguminous plants.

5. **Final Answer**: The organism used as a biofertilizer for raising soybean crop is **Rhizobium**.

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