The chemical fertilizer required for better rhizobial nitrogen fixation is

Options

A. Phosphorus
B. Potassium
C. Calcium
D. Sodium

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds in soil and water. This process is essential for plants as they cannot utilize atmospheric nitrogen directly.

2. **Role of Rhizobium**:
- Rhizobium is a type of bacteria that forms symbiotic relationships with leguminous plants (like peas and beans) to fix nitrogen. The bacteria live in root nodules of these plants and convert atmospheric nitrogen into a form that plants can absorb.

3. **Nutrient Requirements for Nitrogen Fixation**:
- For effective nitrogen fixation, certain nutrients are necessary. These include energy sources (like ATP), reducing agents, and specific enzymes (like nitrogenase).

4. **Identifying the Required Chemical Fertilizer**:
- The question asks for a chemical fertilizer that enhances rhizobial nitrogen fixation. The options provided are phosphorus, potassium, calcium, and sodium.

5. **Analyzing the Role of Phosphorus**:
- Phosphorus is crucial for the growth of plants and plays a significant role in energy transfer (ATP production) and root development. Increased phosphorus levels can enhance the nitrogen-fixing capacity of legume plants by stimulating root production and improving overall plant health.

6. **Conclusion**:
- Based on the analysis, the chemical fertilizer that is required for better rhizobial nitrogen fixation is **phosphorus**.

### Final Answer:
The chemical fertilizer required for better rhizobial nitrogen fixation is **phosphorus**.

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