An organism used as a biofertiliser for raising soyabean crop is

Options

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

Answer

To answer the question regarding the organism used as a biofertilizer for raising soybean crops, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Biofertilizers**:
- Biofertilizers are living organisms that enhance soil fertility by fixing atmospheric nitrogen or decomposing organic matter.

2. **Identify the Organisms Mentioned**:
- The options provided are Azotobacter, Azospirillum, Rhizobium, and Nostoc.

3. **Focus on Leguminous Crops**:
- Soybean is a leguminous crop, which means it belongs to the family of plants that can form symbiotic relationships with nitrogen-fixing bacteria.

4. **Recognize the Role of Rhizobium**:
- Rhizobium is a type of nitrogen-fixing bacteria that specifically associates with the root nodules of leguminous plants, including soybeans.

5. **Explain the Nitrogen Fixation Process**:
- Rhizobium bacteria convert atmospheric nitrogen into ammonia, which is then utilized by the soybean plants for their growth.

6. **Eliminate Other Options**:
- Azotobacter and Azospirillum are nitrogen-fixing bacteria but are typically associated with non-leguminous crops like tea, coffee, and rice. Nostoc is also not specifically associated with soybeans.

7. **Conclude with the Correct Answer**:
- Therefore, the organism used as a biofertilizer for raising soybean crops is **Rhizobium**.

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

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