How Soil Carbon Is Measured on Coffee Farms
Loss on Ignition testing, stratified sampling at 30cm depth, and why below-ground carbon matters as much as above-ground biomass for verified carbon credits.
Above-ground carbon — trees, canopy, biomass — is the visible part of carbon sequestration. But what’s happening below the surface matters just as much. Soil organic carbon (SOC) represents a significant and often underestimated carbon pool, particularly in coffee agroforestry systems.
Why soil carbon matters for coffee
Years of soil sampling across coffee farms in five countries have revealed a common picture: depleted soils with high acidity, imbalanced nutrients (nitrogen, phosphorus, potassium), and a lack of the microbiology that healthy ecosystems depend on.
This degradation is the result of poor land management and, in some cases, excessive fertiliser use. But it also represents opportunity — degraded soils have significant capacity to absorb and store new carbon through regenerative intervention.
Without measuring soil carbon, you’re only seeing half the picture. A coffee farm can be sequestering substantial carbon below ground through improved practices while satellite monitoring only captures the above-ground changes.
How F.O.C.U.S.™ measures soil carbon
The soil measurement methodology uses a two-phase approach:
Baseline establishment
Spectral analysers establish initial soil carbon baselines for each farm. This provides a starting reference point — the carbon level before GAP77™ practices are implemented.
Ongoing monitoring
Loss on Ignition (LOI) testing monitors soil organic carbon changes over time. Soil samples are collected using a stratified W-pattern sampling method — 5 sample points per farm, 3 nested samples at each point, all at 30cm depth using a soil cylinder auger.
This isn’t random sampling. The W-pattern ensures statistical reliability across the plot, and the nested samples at each point account for local variation.
Carbon permanence
The bottom 10cm of each 30cm sample is analysed separately. This tests whether carbon is being stored at depth — where it’s more stable and less likely to be released through surface disturbance. Deep carbon storage indicates genuine long-term permanence rather than shallow accumulation that could be lost.
The carbon stock formula
Soil carbon stock is calculated using IPCC methodology:
Bulk Density × SOC Content × Soil Depth = Carbon per Hectare
Typical bulk density in coffee agroforestry ranges from 1.1 to 1.4 g/cm³. Combined with the SOC percentage from LOI testing and the 30cm sampling depth, this gives a verifiable carbon stock figure for each farm.
Dual measurement: the complete picture
Soil carbon data is combined with above-ground satellite measurements to produce a complete carbon account — both pools measured, both verified, both traceable to individual farms.
This dual approach is what makes F.O.C.U.S.™ carbon credits credible. Each credit represents one metric tonne of CO₂ equivalent backed by real measurement, not modelling.
For the full technical detail, see our carbon measurement methodology. For more on why coffee-specific measurement matters, see our FAQ.
