Crop Rotation Carbon Calculator

The calculator estimates carbon inputs to the soil from crops, green manure, animal manure, and compost, then subtracts estimated carbon mineralisation losses based on your tillage practice and residue management. The result is a net carbon balance expressed in tonnes of CO₂ equivalent per hectare per year, which indicates whether your rotation is building or depleting soil organic matter.

Carbon input is the total organic carbon added to the soil through crops and amendments. Net carbon balance accounts for the carbon lost through microbial mineralisation (decomposition), which converts organic carbon back to CO₂. A positive net balance means your rotation is sequestering carbon; a negative balance means more carbon is leaving the soil than is being added.

Conventional ploughing disrupts soil structure, exposes organic matter to oxygen, and accelerates microbial decomposition, increasing carbon mineralisation rates. Reduced tillage and no-till practices leave soil more undisturbed, slowing mineralisation and helping organic matter accumulate over time. No-till can reduce carbon losses by 20–40% compared to conventional ploughing.

Legumes fix atmospheric nitrogen symbiotically, reducing the need for synthetic nitrogen fertilisers. They also tend to leave high-quality root biomass and residues in the soil. Including legumes as a break crop can boost soil biological activity and slightly increase organic matter inputs, while reducing the carbon footprint of the overall rotation.

The humus equivalent (or humification coefficient) represents the fraction of organic carbon input that is converted into stable humus rather than being mineralised. Different organic materials have different coefficients — compost typically has a high coefficient (~0.5–0.7), while green manure is lower (~0.1–0.2). The calculator uses these factors to estimate how much of each input contributes to long-term soil organic matter.

Yes. Incorporating straw and crop residues after harvest is one of the most practical ways to add organic carbon to soil at no extra cost. Removing or burning straw eliminates this carbon input and can significantly worsen your soil carbon balance over time. Incorporating an average cereal straw crop can add approximately 1–2 t of organic matter per hectare annually.

This tool provides indicative estimates based on published agronomic carbon coefficients and typical mineralisation rates. Actual results will vary depending on soil type, climate, crop yield, management history, and local conditions. For a full farm carbon footprint, consider using a certified tool such as the Farm Carbon Toolkit or commissioning a soil organic carbon survey.

In principle, yes. Practices that measurably increase soil organic carbon — such as introducing cover crops, reducing tillage, or adding organic amendments — can generate credits under voluntary carbon markets (e.g. Soil Carbon Sequestration projects). However, verification requires baseline soil sampling, ongoing monitoring, and third-party auditing. This calculator is intended for planning and learning purposes, not for generating verified carbon credit claims.