Soil

UPSC GS3 — Soil erosion:

Soil erosion: Removal of topsoil by water, wind, or other agents faster than it is formed.

Types:

• Sheet erosion: Thin layer of topsoil removed uniformly by surface runoff — most insidious (invisible)
• Rill erosion: Small channels (rills) carved by concentrated runoff
• Gully erosion: Deep channels carved; creates ravines; "Chambal ravines" in MP/Rajasthan
• Wind erosion: Dry, barren areas; powdery soil blown away; common in Rajasthan, coastlines
• Coastal erosion: Sea waves eroding coastline

Causes of soil erosion:

• Deforestation (roots hold soil; canopy reduces raindrop impact)
• Overgrazing (livestock remove vegetation, expose soil)
• Faulty agricultural practices (ploughing up/down slopes instead of across)
• Flood and heavy rain
• Wind in dry areas

India's soil degradation — authoritative data:

• ISRO Desertification and Land Degradation Atlas (2018-19 data): 97.85 million hectares (29.7% of India's total 328.72 Mha) underwent land degradation — the official satellite-based figure
• Of this, 83.69 million hectares specifically underwent desertification (up from 81.48 Mha in 2003–05 — a worsening 20-year trend)
• Desertification increased in 28 of 31 states/UTs monitored
• Rajasthan tops with 21.23 Mha desertified; Maharashtra second at 14.3 Mha
• 5.3 billion tonnes of soil lost annually through water erosion — ICAR
• Waterlogging + salinisation in canal-irrigated areas (Punjab-Haryana: Green Revolution's negative legacy)

[Additional] Soil Organic Carbon (SOC) and climate change:

• Soil is the world's largest terrestrial carbon store — soils hold ~2,500 gigatonnes of carbon, roughly 3× the amount in the atmosphere and 4× the amount in all living vegetation
• When topsoil erodes or organic matter declines, stored carbon is released as CO₂ → contributes to climate change
• "4 per 1000" Initiative (launched by France at COP21, Paris 2015): If global soil organic carbon content increased by 0.4% (4 per 1,000) per year, it would offset all annual global CO₂ emissions from fossil fuels — illustrating soil's potential as a climate mitigation tool
• India has not formally joined the 4 per 1000 initiative, but improving SOC through organic farming, cover crops, and reducing tillage is increasingly emphasised in India's agricultural policy (PM Pranam, Natural Farming Mission)

Conservation measures:

• Contour ploughing: Plough across slope (along contour lines) rather than up/down → reduces runoff
• Terracing: Cut steps into hillside → reduces slope; allows cultivation without erosion
• Shelter belts: Rows of trees planted around fields → reduce wind erosion (Rajasthan, Punjab)
• Afforestation: Planting trees → roots hold soil; canopy reduces rain impact
• Cover crops: Plant vegetation even in fallow season to keep soil covered
• Check dams: Small dams in ravines slow water → reduces gully erosion; stores water
• Bunding: Earthen embankments around fields to retain rainwater + reduce runoff

[Additional] Key Government Schemes for Soil Health:

• Soil Health Card (SHC) Scheme (2015): Every farmer receives a card with soil nutrient status and recommended fertilizer doses — reduces over-application of chemical fertilizers and soil acidification. Over 23 crore SHCs distributed across two cycles.
• PM Pranam Scheme (2023): PM Programme for Restoration, Awareness, Nourishment, and Amelioration of Mother Earth — incentivizes states to reduce chemical fertilizer use; 50% of savings in fertilizer subsidy given back to the state for soil restoration.
• National Mission for Sustainable Agriculture (NMSA): Part of NAPCC; focuses on soil health management, organic farming, watershed development.
• [Additional] Land Degradation Neutrality (LDN): India's commitment under UNCCD (UN Convention to Combat Desertification) — target to restore 26 million hectares of degraded land by 2030 and neutralise further degradation. NITI Aayog coordinates restoration.