UPSC Prelims 2012 Q98: Environment & Ecology – Biodiversity & Conservation
- (a) 1 and 2 only
- (b) 3 only
- (c) 1, 2 and 3
- (d) None of them
Answer: (b) 3 only
Explanation
Farm practices and carbon storage in soil
Carbon sequestration in soil means keeping carbon locked in the soil as organic matter and not letting it escape as carbon dioxide.
| Practice | What it is | Helps store carbon in soil? |
|---|---|---|
| 1. Contour bunding | Small earthen banks along the contour of a slope | Not counted; it is a soil and water conservation measure |
| 2. Relay cropping | Sowing the next crop before the first is harvested | Not counted; it is a way of raising cropping intensity |
| 3. Zero tillage | Sowing without ploughing, into the stubble | Yes; unploughed soil does not release its carbon, and crop residue adds more |
Why ploughing matters: tillage exposes soil organic matter to air, and microbes turn it into carbon dioxide.
Other practices that store carbon:
| Practice | How |
|---|---|
| Mulching and residue retention | Adds organic matter |
| Agroforestry | Trees store carbon above and below ground |
| Cover crops | Keep the soil covered all year |
Note: some teachers argue that all three help a little, but the accepted answer is zero tillage alone.
Answer: (b) 3 only.
Why each option is right or wrong
- (a) Incorrect. Contour bunding and relay cropping are not carbon storage practices, and zero tillage is left out.
- (b) CORRECT. Zero tillage keeps carbon locked in the soil.
- (c) Incorrect. Contour bunding and relay cropping serve other purposes.
- (d) Incorrect. Zero tillage does help in carbon sequestration in the soil.
Key point
Zero tillage (conservation agriculture): no ploughing, residue kept, soil carbon retained. Contour bunding: erosion control. Relay cropping: overlapping crops for higher intensity.
Remember
Zero tillage = soil carbon stays put.
Common mistakes
- Marking all three because every good farm practice seems climate-friendly.
- Not knowing what relay cropping is; it is about timing of crops.
- Confusing contour bunding (saves soil and water) with carbon storage.
Exam tip
Ask what each practice is designed for. Only zero tillage is aimed at leaving the soil, and its carbon, undisturbed.
Sources
- Food and Agriculture Organization — Conservation Agriculture and soil carbon sequestration
- Indian Council of Agricultural Research — Conservation agriculture and zero tillage in the rice-wheat system