Which one of the following can be used as biofertiliser in cotton field?

Options

A. Azolla-Anabaena
B. Streptococcus
C. Azospirillum
D. Azotobacter chroococcum

Explanation

To determine which of the given options can be used as a biofertilizer in cotton fields, we will analyze each option step by step.

### Step 1: Understand Biofertilizers
Biofertilizers are natural fertilizers that contain living microorganisms, which promote the growth of plants by increasing the availability of nutrients. They can help in nitrogen fixation, phosphorus solubilization, and enhancing soil fertility.

### Step 2: Analyze Each Option
1. **Azolla and Anabaena**:
- Azolla is a water fern that forms a symbiotic relationship with the cyanobacterium Anabaena.
- This association is primarily used in rice cultivation due to its ability to fix atmospheric nitrogen.
- **Conclusion**: Not suitable for cotton fields.

2. **Streptococcus**:
- Streptococcus is a genus of bacteria that is not typically used as a biofertilizer.
- It is more known for its role in human and animal health rather than in agriculture.
- **Conclusion**: Not suitable for cotton fields.

3. **Azoospirillum**:
- Azoospirillum is a genus of bacteria that can promote plant growth by fixing nitrogen and enhancing nutrient uptake.
- It is known to associate with various plants, including some crops, but it is not the most common choice for cotton.
- **Conclusion**: While it can be beneficial, it is not the best option specifically for cotton.

4. **Azotobacter crococum**:
- Azotobacter is a free-living nitrogen-fixing bacterium found in the soil.
- It is known for its ability to enhance soil fertility and is commonly used as a biofertilizer for various crops, including cotton.
- **Conclusion**: This is a suitable biofertilizer for cotton fields.

### Step 3: Final Answer
Based on the analysis, the best option that can be used as a biofertilizer in cotton fields is **D. Azotobacter crococum**.

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