Which one statement is correct?

Options

A. Cyanobacteria, such as Anabaena and Nostoc are important mobilisers of phosphates and potassium for plant nutrition in soil.
B. At present, it is not possible to grow maize without chemical fertilisers.
C. Extensive use of chemical fertilisers may lead to eutrophication of nearby waterbodies.
D. Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants

Answer

To determine which statement is correct among the four given options, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Evaluate the First Statement:**
- The statement claims that cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and potassium for plant nutrition in soil.
- **Analysis:** This statement is incorrect. Anabaena and Nostoc are known for their ability to fix nitrogen, not for mobilizing phosphates and potassium.

2. **Evaluate the Second Statement:**
- The statement suggests that it is not possible to grow maize without chemical fertilizers.
- **Analysis:** This statement is also incorrect. Maize can be grown without chemical fertilizers by using organic manures and compost as alternatives.

3. **Evaluate the Third Statement:**
- The statement indicates that extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.
- **Analysis:** This statement is correct. The runoff from fields treated with chemical fertilizers can lead to nutrient enrichment in water bodies, causing algal blooms and eutrophication.

4. **Evaluate the Fourth Statement:**
- The statement claims that Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants.
- **Analysis:** This statement is incorrect. While Rhizobium does fix nitrogen in symbiotic root nodules of legumes, Azotobacter is a free-living bacterium in the soil that also fixes nitrogen but does not form nodules.

### Conclusion:
After analyzing all four statements, the correct statement is:
- **Option C:** Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.