Soil sample data requirements

After you've taken soil samples from your fields and sent them to the lab for analysis, you can share the results with Regrow so they can be applied to predict the soil properties needed to initialize DNDC for the remaining, non-sampled fields. 

The following sections explain the data needed by Regrow and how it's used to model soil properties on program fields. 

Considerations & data requirements for labs

Sampling depth and layer requirements

• Required layer: Results for a layer equivalent to 0–30 cm (± 1 cm) is required
  • If your field protocol collects cores in increments (example: 0–15cm and 15–30cm), please share the data for each layer separately, but the lab must also report a combined 0–30 cm set of soil properties so there is one complete record representing 0–30 cm
• Optional additional layers: Cores at additional depth layers are allowed and can improve future analyses (ex: ESM sampling)
  • It’s helpful to share these with Regrow when available, but are not required to be shared
  • If you sample to multiple depths, include a separate row for each depth interval, where sample IDS and coordinates will remain the same for all cores taken at the location
    • See the template linked above for an example of this
• ⚠️ Important note: if you sample deeper than 30cm, bulk density must be measured and reported for 0–30 cm
• SOC measurements may be based on combined deeper cores, per Verra’s VM0042 protocol

Required data & lab measurement considerations

Please refer to the template linked above for all relevant data requirements, as well as formatting requirements and descriptions. Below are additional considerations for measurement requirements that may be helpful before lab processing begins.

Sample identifiers and locations

• Sampled location coordinates: Coordinate precision matters! Avoid rounding coordinates. Each decimal increases location precision, which is important for soil modeling
• Provide the instrument used to measure coordinates when possible. This helps in understanding precision

• Why this matters: Sample IDs and planned coordinates help Regrow align samples if different properties were measured using different cores taken near each other (for example, SOC and bulk density sampled ~1 m apart)

Bulk density and coarse fragments (critical)

Bulk density is a key soil property for soil modeling. Special considerations need to be taken when soils are rocky.

Coarse fragment % is a required data point because it determines whether bulk density calculations must be adjusted to account for the presence of the fragments (common in rocky soils)

• If coarse fragments are ≤ 2–3%: Reporting Total Dry Bulk Density is acceptable
• If coarse fragments are > 2–3%: Regrow strongly recommends the lab provide a Fine Bulk Density calculation (as a recommended best practice)

Fine Bulk Density

• Fine bulk density should be provided for all fields with high coarse fragment
  • Please include total dry bulk density for all fields, regardless
• Calculating fine bulk density generally requires a volume-correction method (ie displacement) to adjust the sample volume after removing coarse fragments
• ⚠️ Important! This may add lab time/cost and should be discussed with the lab upfront

• If the lab cannot provide Fine Bulk Density, Regrow can apply a mass-correction to estimate a hybrid bulk density
  • For Labs: if this is the chosen direction, the lab must provide the coarse fragment percent, and estimated carbon stock to enable the bulk density adjustment

⚠️ For project developers: this can increase audit risk because mass adjustments alone may not reliably represent volume differences (for example, small but very dense fragments will impact density differently than large and light ones).