Correct Option
The correct option is (b) 2, 3 and 4 only.
Explanation
Soil degradation refers to the decline in soil quality caused by its improper use or poor management, usually for agricultural, industrial, or urban purposes. It involves the physical, chemical, and biological deterioration of soil. Conversely, soil conservation methods aim to protect soil from erosion and maintain its fertility.
Statement-wise Analysis
- 1. Mulching: Incorrect. Mulching is a soil conservation method, not a cause of degradation. It involves covering the bare ground between plants with a layer of organic matter like straw. This helps retain soil moisture, suppresses weeds, and prevents soil erosion.
- 2. Overgrazing: Correct. Overgrazing by livestock removes the vegetative cover that protects the soil. Without grass and roots to bind the soil, it becomes loose and highly susceptible to erosion by wind and water, leading to degradation.
- 3. Rain wash: Correct. Rain wash refers to the removal of the top layer of soil by the force of running water (surface runoff). This is a primary form of soil erosion, which physically degrades the land by stripping away nutrient-rich topsoil.
- 4. Overuse of chemical fertilisers: Correct. Excessive use of chemical fertilisers alters the natural chemical balance of the soil. It can kill beneficial soil microorganisms, increase soil acidity or alkalinity, and reduce long-term fertility, thereby causing chemical degradation.
Key Takeaway: Soil degradation is driven by factors like deforestation, overgrazing, rain wash, and chemical overuse, whereas techniques like mulching, contour barriers, and terrace farming are used for soil conservation.