Conservation Tillage Carbon Balance

Field Management

Tillage intensity 0.20 (reduced)

Cover-crop carbon input 2.0 Mg C/ha/yr

Simulation speed 4 yr/s

Soil Carbon

Years elapsed

0.0 yr

SOC stock

40.0 Mg/ha

Sequestration rate

+0.00 Mg/ha/yr

Equilibrium SOC

— Mg/ha

Decomposition constant k

— /yr

How it works

Soil organic carbon (SOC) is modelled as a single well-mixed pool with first-order decomposition — the same Hénin–Dupuis form used inside steady-state soil-carbon models like RothC:

dC/dt = I − k·C
C_eq  = I / k   (steady-state SOC)

where C is the SOC stock (Mg C/ha), I is the annual carbon input from cover-crop residue plus a small baseline crop-residue input, and k is the fractional decomposition rate. Tillage does not remove carbon directly — it accelerates k by breaking soil aggregates open, exposing protected organic matter to microbial attack and oxygen:

k = k0 · (1 + β·tillage)
k0 ≈ 0.020 /yr  (intact, undisturbed aggregates)
β  ≈ 2.5        (aggregate-disruption sensitivity)

Tillage intensity — 0 is no-till (soil left undisturbed, aggregates intact, low k); 1 is intensive conventional tillage (full inversion every year, aggregates broken, high k). A visible plow pass sweeps the field once per simulated year whenever tillage > 0.05.
Cover-crop carbon input — the extra biomass-carbon returned to the soil each year by a cover crop; higher input raises the equilibrium SOC stock C_eq = I/k and is shown growing on the field between tillage passes.
Sequestration rate — the instantaneous dC/dt: positive while SOC is below equilibrium (building carbon), negative while above it (losing carbon, e.g. after switching from no-till to intensive tillage).

Real-world relevance: this is the mechanism behind why no-till plus cover crops is the standard prescription for regenerative-agriculture carbon credits — cutting k by leaving soil undisturbed sequesters carbon even without changing how much residue is returned.

Soil carbon column Cover-crop canopy Plow pass (tillage event)

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