Parameters shown in Soil Carbon Check

All decomposed organic material in the soil, derived from plants, roots, manure and microorganisms. SOM contains carbon, oxygen, hydrogen, nitrogen, phosphorus and sulphur.

SOM feeds soil life and drives nutrient cycling, water retention and soil structure. It is one of the most important indicators of soil health.

Organic matter decomposes through soil organisms. The process slows down over time, and it can take decades for new material to stabilise as humus.

The carbon fraction of organic matter and the central measurement in Soil Carbon Check.

SOC reflects the amount of carbon stored in the soil and how much CO₂ is removed from the atmosphere. Higher SOC means improved soil fertility and resilience.

Inorganic or mineral carbon in the soil, formed from weathering or carbonate minerals.

SIC contributes to total carbon storage but is less dynamic than organic carbon and changes more slowly over time.

SOC can be expressed as CO₂ equivalents using a factor of 3.67 (44/12 molar ratio).

This allows soil carbon storage to be linked directly to climate impact and greenhouse gas reduction.

Represents the carbon proportion within total organic matter, typically ranging from 45–60%.

Higher percentages indicate more stable organic matter that decomposes more slowly, enhancing long-term soil carbon sequestration.

The sum of organic (SOC) and inorganic (SIC) carbon in the soil.

Total carbon represents the overall carbon reserve of the soil, important for understanding storage capacity and soil health trends.

The small, highly reactive portion of SOC (about 1–4%) that responds quickly to management changes.

Measured with the permanganate-oxidizable carbon (POXC) method as a proxy for active SOC.

Increases with practices like cover cropping, reduced tillage and legume use — indicating healthier, more biologically active soil.

Expresses the balance between carbon and nitrogen in organic matter.

A low C/N ratio leads to faster decomposition and nutrient release, while a high ratio slows breakdown but enhances carbon stability.

Farm inputs such as straw or solid manure tend to increase the C/N ratio over time.

Shows the balance between carbon and sulphur in soil organic matter.

A low C/S ratio indicates good sulphur mineralisation and nutrient availability, while a high ratio signals less active decomposition.

Soil particles smaller than 2 µm with a large surface area and nutrient-holding capacity.

Clays store nutrients like magnesium, potassium and calcium, and improve water retention and soil fertility. Different clay types vary in activity and structure.

Relates clay content to organic carbon, serving as an indicator of soil structure quality.

A ratio of around 8:1 indicates excellent soil structure; values of 13:1 or higher suggest poorer aggregation and increased compaction risk.

The dry weight of soil per unit volume, influenced by texture, organic matter and compaction.

Used to calculate total soil mass and carbon stock per hectare. Soil Carbon Check predicts bulk density via a pedotransfer function (Hollis et al., 2012).

Estimates how much SOC is expected to decompose during the coming season.

Calculated with the MINIP model (Yang, 1996; Yang & Janssen, 2000), which simulates organic matter breakdown.

Shows how much SOC needs to be replenished to maintain or increase carbon storage.

The “4 per mille” (4‰) initiative, launched at COP21, aims to offset global CO₂ emissions by increasing SOC in agricultural soils by 0.4% annually.

Soil Carbon Check calculates how much additional organic carbon input is needed per hectare to reach this target.