Soil carbon sequestration

How it works

Plants pull atmospheric CO₂ through photosynthesis. Some of this carbon is:

• Eaten and returned quickly through respiration
• Decomposed in surface litter — short-lived
• Incorporated into [[soil-organic-matter|soil organic matter]] — varying durability
• Stabilized as humus or biochar-like compounds — centuries to millennia

The fraction stabilized depends substantially on management practices:

• Tillage disrupts soil aggregates and exposes organic matter to oxidation; releases stored carbon
• [[cover-cropping|Cover cropping]] keeps roots growing and soil covered; builds carbon
• Diverse rotations and polycultures support diverse soil biology; build complex organic matter
• Livestock integration at appropriate density adds carbon and stimulates soil biology
• Perennials (in agroforestry, silvopasture, food forests) build deep root carbon for years
• No external inputs allows soil biology to function fully

Magnitudes

• Global soil organic carbon stock — ~1,500-2,400 gigatons (varies by depth measured)
• Atmospheric CO₂ stock — ~880 gigatons carbon equivalent
• Pre-agricultural soil carbon — many cultivated soils have lost 30-75% of their original carbon
• Recovery potential — substantial; cultivated soils worldwide could absorb tens of gigatons

The “4 per 1000” Initiative

Launched at COP21 in 2015 by the French government:

• Proposal — increase global soil organic carbon by 0.4% annually
• Mathematical effect — 4‰ × global stock = ~6 gigatons C/year, comparable to annual fossil-fuel emissions
• Pragmatic reality — not achievable globally, but substantial progress possible in many regions
• Network — 600+ partners worldwide working on the initiative

Practices and rates

Documented annual soil-carbon-building rates by practice:

• Conventional cropping — typically losing carbon (declining)
• [[cover-cropping|Cover cropping]] — gain of 0.3-1.0 tons C per hectare per year
• [[no-till-farming|No-till]] + cover crops — gain of 0.5-1.5 tons C per hectare per year
• Perennial pasture / well-managed grazing — gain of 0.5-2.0 tons C per hectare per year
• Agroforestry — gain of 1.0-3.0 tons C per hectare per year (above and below ground)
• Holistic-grazed grasslands — variable; documented gains 1-7 tons C per hectare per year in best cases

Caveats

• Sequestration is not unlimited — soils saturate at some carbon level; gains slow over time
• Reversible — practices stop, carbon can rapidly re-release
• Permanence concerns — for carbon-credit accounting
• Methane and nitrous oxide trade-offs — some practices that build soil carbon also produce other greenhouse gases
• Not a silver bullet — supplements emission reductions, doesn’t replace them

Why this matters

Soil-carbon building combines climate mitigation with soil health, water-holding capacity, fertility, biodiversity, drought resilience. The co-benefits make it economically attractive even without carbon credits. For 0mn1.one’s framing of [[regenerative-agriculture|regenerative agriculture]] as foundational, soil-[[carbon-sequestration|carbon sequestration]] is the climate dimension of practices already worth doing for ecological and economic reasons.

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

• Subset of: [[carbon-sequestration]]
• Shares approach with: [[cover-cropping]] · [[holistic-planned-grazing]]

Sources

• 4 per 1000 Initiative published materials
• Lal, R. multiple soil-carbon publications
• IPCC AR6 Working Group III on agriculture and land use

Rooted in life.