A Crop rotation decreases the soil fertility.
R High concentration of minerals is required as fertilizers.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Crop rotation decreases the soil fertility."
- To analyze this, we need to understand what crop rotation is. Crop rotation involves growing different types of crops in the same area in sequential seasons.

2. **Evaluating Crop Rotation**:
- Crop rotation is beneficial as it helps maintain soil fertility. Different crops have varying nutrient requirements and growing legumes, for example, can help fix nitrogen in the soil, enhancing its fertility.

3. **Conclusion on Assertion**:
- Since crop rotation does not decrease soil fertility but rather helps in maintaining or even increasing it, the assertion is **false**.

4. **Understanding the Reason**:
- The reason states that "High concentration of minerals is required as fertilizers."
- This implies that all crops require a large amount of minerals to grow, which is not entirely accurate.

5. **Evaluating Nutrient Requirements**:
- Different crops have specific nutrient requirements. For instance, legumes may require less nitrogen due to their ability to fix atmospheric nitrogen. Therefore, not all crops need high concentrations of minerals.

6. **Conclusion on Reason**:
- Since the statement about high concentrations of minerals being universally required as fertilizers is also misleading, the reason is **false**.

7. **Final Conclusion**:
- Both the assertion and the reason are false. Therefore, the correct answer is that both statements are incorrect.