Consider the following agricultural practices: 1. Contour bunding 2. Relay cropping 3. Zero tillage In the context of global climate change, which of the above helps/help in carbon sequestration/storage in the soil?
Contents23
- A1 and 2 only
- B3 only
- C1, 2 and 3
- DNone of them
Show answer
Answer: (C) 1, 2 and 3
All three agricultural practices help in carbon sequestration in soil:
Contour bunding (statement 1) — reduces soil erosion, retaining organic matter and carbon in the soil.
By preventing topsoil from washing away, carbon stored in the soil is preserved.
Relay cropping (statement 2) — ensures continuous plant cover on the soil.
Growing a second crop before the first is harvested keeps roots in the ground longer, adding organic matter and keeping carbon locked in the soil.
Zero tillage (statement 3) — by not ploughing/tilling the soil, carbon-rich organic matter is not disturbed and remains stored.
Tillage exposes soil carbon to air, converting it to CO₂.
All three reduce carbon release and/or increase carbon storage in soil.
Answer: 1, 2 and 3.
Soil carbon storage is critical because soils contain more carbon than the atmosphere and vegetation combined, making agricultural practices key to climate mitigation.
UPSC is testing whether students understand that carbon sequestration happens through preventing soil disturbance, maintaining plant cover, and reducing erosion - not just through tree planting.
The question requires knowing the specific mechanisms: contour bunding prevents carbon loss through erosion, relay cropping maintains root systems that add organic matter, and zero tillage avoids releasing stored soil carbon to the atmosphere.
Contour Bunding
Environment Contour bunding
Contour Bunding: Erosion Control & Carbon Storage
Contour bunding means building ridges/barriers across slopes following the natural contour lines
Prevents soil erosion by slowing water flow down slopes
Helps carbon sequestration by retaining topsoil with organic matter
Widely used in hilly and semi-arid regions of India
What is Contour Bunding
Contour bunding involves constructing small earthen ridges or stone barriers along the natural slope contours of farmland. These bunds act like speed breakers for water flowing down slopes during rainfall.
How It Prevents Soil Loss
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Rainfall on sloped land**
Water naturally flows downhill, gaining speed`"]
s2["`**Contour bunds intercept water**
Ridges built across slope slow water flow`"]
s3["`**Water pools behind bunds**
Reduced velocity allows soil particles to settle`"]
s4["`**Topsoil retained on field**
Carbon-rich organic matter stays in place`"]
s1 --> s2
s2 --> s3
s3 --> s4Carbon Storage Benefits
Topsoil retention — prevents carbon-rich surface soil from washing away
Organic matter preservation — decomposed plant material stays in field instead of eroding
Water infiltration — bunds allow more water to soak into soil, supporting plant growth and root carbon
Trap: Thinking contour bunding only controls water, not carbon — it does both by preventing soil loss
Trap: Confusing with terracing — terracing creates flat steps, contour bunding just slows water flow
Relay Cropping
Environment Relay cropping
Relay Cropping: Continuous Plant Cover System
Relay cropping means planting a second crop before the first crop is harvested
Ensures continuous plant cover on soil throughout the year
Maximizes carbon input from roots and prevents carbon loss
Common example: wheat-rice relay in northern India
Relay vs Other Systems
Relay cropping differs from regular cropping because the second crop is planted before harvesting the first. This overlapping period ensures soil is never left bare, unlike sequential cropping where fields stay empty between harvests.
Cropping System Comparison
System | Timing | Soil Cover | Carbon Impact |
|---|---|---|---|
Sequential cropping | Crop 2 planted after Crop 1 harvest | Gaps between crops | Carbon lost during bare periods |
Relay cropping | Crop 2 planted before Crop 1 harvest | Continuous cover | Maximum carbon retention |
Intercropping | Two crops grown together | Full cover during season | Good carbon input but seasonal |
Carbon Sequestration Mechanism
Living roots year-round — roots continuously add organic matter to soil
No bare soil periods — prevents carbon oxidation when soil is exposed to air
Higher biomass production — more plant matter means more carbon input
Trap: Thinking relay cropping is just about yield — it's also about continuous soil cover
Trap: Confusing with mixed cropping — relay involves time overlap, mixed involves space sharing
Zero Tillage
Environment Zero tillage
Zero Tillage: No-Plough Farming for Carbon Storage
Zero tillage means planting crops without ploughing or disturbing the soil
Maximum carbon sequestration among all tillage practices
Prevents soil carbon oxidation that happens when soil is turned over
Part of conservation agriculture promoted in India
Why Tillage Releases Carbon
When soil is ploughed, buried organic matter gets exposed to oxygen. This causes soil carbon to oxidize into CO₂ and escape to the atmosphere. Zero tillage keeps this carbon locked underground.
Tillage Methods & Carbon Impact
Method | Soil Disturbance | Carbon Effect | Usage |
|---|---|---|---|
Conventional tillage | Full ploughing + harrowing | High carbon loss | Traditional farming |
Minimum tillage | Reduced ploughing | Moderate carbon loss | Compromise approach |
Zero tillage | No soil disturbance | Maximum carbon storage | Conservation agriculture |
Carbon Loss in Conventional Tillage
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flowchart TD
s1["`**Ploughing breaks soil structure**
Tractor turns over topsoil layers`"]
s2["`**Organic matter exposed to air**
Previously buried carbon comes into contact with oxygen`"]
s3["`**Microbial oxidation accelerates**
Bacteria break down organic matter faster`"]
s4["`**CO₂ released to atmosphere**
Soil carbon converted to greenhouse gas`"]
s1 --> s2
s2 --> s3
s3 --> s4Additional Benefits
Soil structure preservation — maintains natural pore spaces for water and air
Reduced fuel consumption — no tractors for ploughing saves diesel
Earthworm activity — undisturbed soil supports beneficial organisms
Trap: Thinking zero tillage reduces crop yield — modern techniques maintain good yields
Trap: Assuming minimum tillage is the same as zero tillage — minimum still disturbs some soil
Soil Carbon Sequestration
Environment carbon sequestration carbon storage
Soil Carbon Sequestration: Climate Change Mitigation
Soil carbon sequestration means storing atmospheric CO₂ in soil as organic matter
Soils store 3x more carbon than the atmosphere globally
Agricultural practices can either increase or decrease soil carbon storage
Key strategy for climate change mitigation in agriculture
Why Soil Carbon Matters
Soil organic carbon comes from decomposed plant and animal matter. When agricultural practices disturb soil or remove plant cover, this stored carbon gets released as CO₂. Smart farming can reverse this process.
Carbon Sequestration Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Plants absorb CO₂ from air**
Photosynthesis converts atmospheric carbon to plant matter`"]
s2["`**Roots and leaves add organic matter**
Dead plant parts become soil organic matter`"]
s3["`**Microbes partially decompose material**
Some carbon released, some forms stable compounds`"]
s4["`**Stable carbon stored in soil**
Long-term storage removes CO₂ from atmosphere`"]
s1 --> s2
s2 --> s3
s3 --> s4Practices That Increase vs Decrease Soil Carbon
Increase Carbon Storage | Decrease Carbon Storage | Impact |
|---|---|---|
Zero tillage | Conventional ploughing | Tillage exposes carbon to oxidation |
Cover crops/relay cropping | Bare fallow periods | Continuous roots add organic matter |
Crop residue retention | Stubble burning | Burning releases all carbon as CO₂ |
Contour bunding | Uncontrolled erosion | Erosion washes away carbon-rich topsoil |
Global Significance
4 per 1000 initiative — global goal to increase soil carbon by 0.4% annually
Carbon credits — farmers can earn money for verified soil carbon storage
Food security co-benefit — carbon-rich soils are more fertile and productive
Trap: Thinking only forests sequester carbon — agricultural soils have huge potential too
Trap: Assuming carbon sequestration always requires new technology — traditional practices like cover crops work
Conservation Agriculture in India
Environment
Conservation Agriculture: India's Climate-Smart Farming
Conservation Agriculture promoted under National Mission on Sustainable Agriculture
Focus on zero tillage, crop residue retention, and crop diversification
Punjab and Haryana leading adoption due to stubble burning concerns
Addresses climate change adaptation and mitigation simultaneously
Policy Context
India promotes Conservation Agriculture (CA) as part of climate-smart farming. The approach combines productivity goals with environmental benefits like carbon sequestration and reduced greenhouse gas emissions.
Conservation Agriculture Principles
# Conservation Agriculture
## Minimal Soil Disturbance
- Zero tillage
- Reduced tillage
- Direct seeding
## Permanent Soil Cover
- Crop residue retention
- Cover crops
- Mulching
## Crop Diversification
- Crop rotation
- Relay cropping
- IntercroppingCA Adoption in Major States
State | Main Focus | Driver | Challenge |
|---|---|---|---|
Punjab | Zero tillage in rice-wheat | Stubble burning reduction | Farmer mindset change |
Haryana | Happy Seeder technology | Air pollution control | Equipment cost |
Uttar Pradesh | Crop diversification | Soil health improvement | Market access |
Madhya Pradesh | Residue management | Water conservation | Technical knowledge |
Government Schemes
Sub-Mission on Agricultural Mechanization — provides subsidies for CA equipment
National Mission for Sustainable Agriculture — promotes CA practices
Crop Residue Management scheme — financial assistance to avoid stubble burning
Trap: Thinking CA is only about zero tillage — it requires all three principles together
Trap: Assuming CA is new in India — traditional practices like mixed cropping are CA principles