Sandy v5.1.5 – Residues Model Update & Bayesian Soil Carbon Inclusion

1. Major Update to Arable & Horticulture Residue Methods

This release introduces a substantial upgrade to how Sandy calculates crop residues, residue management emissions, and soil carbon impacts in arable and horticultural systems.

What has changed?

• Improved dry matter assumptions across a wide range of crops and residues

• Residue moisture content is now user-adjustable

• New internal residue management methods for methane (CH₄) and nitrous oxide (N₂O)

• Updated soil carbon calculations to incorporate revised residue data and better reflect residue removal vs. retention practices

• Structural improvements to make the residues model more flexible and maintainable

This update will change results, in some cases materially, for residue management CH₄, residue management N₂O, and soil carbon stock change (CO₂).

Users must sync and re-run calculations to apply the update.

2. Scientific Basis for the Residue Update

Previous residue and soil carbon methods were closely aligned with the 2019 IPCC Guidelines. Further review highlighted limitations in default dry matter assumptions. A detailed literature review found several IPCC default parameters were atypical relative to more recent peer-reviewed evidence, particularly for horticultural crops and temporary systems.

Dry matter assumptions have therefore been comprehensively revised, and Trinity now operates a fully proprietary, in-house residue model grounded in contemporary literature.

This update represents a genuinely exciting and sector-leading innovation for the fresh produce industry. For the first time, growers of leafy-greens, vegetables, soft fruit and short-rotation crops can robustly quantify and confidently communicate the soil carbon sequestration impacts of their production systems. By rebuilding the residues model from the ground up, Trinity enables fresh produce businesses to demonstrate their measurable contribution to soil carbon outcomes, unlocking a powerful narrative for retailers and brands.

3. Nature and Direction of Result Changes

3.1 Dry Matter Revisions

Revised dry matter content affects how yields are converted into residue mass. In most cases, dry matter values have reduced, lowering the total residue entering emissions and soil carbon calculations.

Users may override default dry matter values from Sandy’s UI, if they have their own robust farm-specific data available, though Trinity recommends using the updated defaults, which have been through significant testing.

3.2 Expected Emissions Impacts

• Nitrous oxide (N₂O) from residues is likely to reduce
• Methane (CH₄) from residue management is likely to reduce
• Soil carbon stock change magnitude may reduce

3.3 Crop Groups Most Affected

Updates focus particularly on horticultural leafy-greens, soft fruit, horticultural vegetables, temporary grassland and cover crops.

3.4 Residue Management Logic Update

Internal logic has been strengthened to ensure consistency between above and below-ground residues and soil carbon accounting. Residues removed from the field no longer contribute to soil organic matter pools.

4. Soil Carbon Update: Bayesian Model–Data Fusion Framework

Sandy now includes a formal Bayesian calibration framework within its soil carbon module. The model simulates soil organic carbon (SOC) stocks and changes under user-specific cropping, management, climate and soil conditions.

Where measured soil carbon data are provided, Sandy combines observations with model outputs to update estimates and confidence intervals, improving accuracy and uncertainty quantification.

The introduction of Bayesian calibration marks a step-change for users seeking to participate in high-integrity carbon and removals projects. By formally integrating measured soil carbon data with a process-based, IPCC-derived model through a statistically coherent framework, Sandy delivers industry-leading, high-fidelity calculations with transparent uncertainty quantification.

Users can now choose which soil method they would like to report against to allow for full flexibility aligned with the requirements of their chosen reporting standard. 

5. Bayesian Calibration for Removals Projects

For formal removals project modelling, Sandy supports Bayesian calibration of initial soil carbon pool states in alignment with standards such as Verra VMD0053 and the Climate Action Reserve Soil Enrichment Protocol.

Structural and kinetic model parameters remain fixed at independently validated values, while uncertainties in residue inputs are treated as informed priors. Measured SOC data update these priors to generate posterior distributions, constraining uncertainty and preserving biogeochemical integrity.

6. Backwards Compatibility

No structural back-compatibility issues have been identified. Users must sync and re-run calculations to see updated results.

Summary

This release represents a major methodological upgrade to Sandy:

• More accurate crop residue characterisation
• Improved treatment of residue removal
• Reduced reliance on IPCC default dry matter assumptions
• Fully proprietary residue model
• Introduction of Bayesian SOC calibration for removals projects
• Enhanced uncertainty quantification

These changes further strengthen both scientific robustness and future model flexibility, ensuring Sandy remains aligned with evolving literature, standards, and client needs.

If you have questions about how this update affects your results, please contact the Customer Success team via customer.success@trinityagtech.com