Which of the following increase the fertillity of soil ?
A) Lactobacillus bacteria B)Rhizobium bacteria C)Spirogyra algae D) Blue - green algae

Options

A. A and B
B. B and C
C. A and D
D. B and D

Answer

To determine which of the given options increases the fertility of soil, we will analyze each option step by step.

### Step 1: Analyze Lactobacillus bacteria
- **Explanation**: Lactobacillus bacteria are primarily known for their role in the fermentation of milk and production of yogurt. They do not have a significant impact on soil fertility.
- **Conclusion**: Lactobacillus does not increase soil fertility.

### Step 2: Analyze Rhizobium bacteria
- **Explanation**: Rhizobium bacteria are found in the root nodules of leguminous plants. They have the unique ability to fix atmospheric nitrogen, converting it into a form that plants can use. This process enriches the soil with nitrogen, which is essential for plant growth.
- **Conclusion**: Rhizobium significantly increases soil fertility.

### Step 3: Analyze Spirogyra algae
- **Explanation**: Spirogyra is a type of green algae found in freshwater environments. While it contributes to aquatic ecosystems, it does not play a role in enhancing soil fertility.
- **Conclusion**: Spirogyra does not increase soil fertility.

### Step 4: Analyze Blue-green algae
- **Explanation**: Blue-green algae, also known as cyanobacteria, can fix nitrogen from the atmosphere. They can also contribute to the availability of potassium and phosphorus in the soil. This ability makes them beneficial for soil fertility.
- **Conclusion**: Blue-green algae can increase soil fertility.

### Final Conclusion
- The options that increase soil fertility are **B) Rhizobium bacteria** and **D) Blue-green algae**. However, the most direct answer to the question is **B) Rhizobium bacteria**, as it is specifically known for its role in nitrogen fixation in the soil.