Verra wishes to remind proponents of projects using Verified Carbon Standard (VCS) Program methodology VM0042 Improved Agricultural Land Management that they must use soil data that meets the minimum sampling depth requirement of 30 centimeters for model inputs (qualification approach 1) or measured values (qualification approach 2) for ex post quantification of soil organic carbon (SOC) stock changes.
The 30 cm depth for soil carbon stock quantification is a standard used by the Intergovernmental Panel on Climate Change to estimate and report changes in SOC stocks in mineral soils, as the top 30 cm is most impacted by land management changes. Relying on data from shallower depths increases the uncertainty of the impact of agricultural land management practices.
This requirement also applies to data measured to less than 30 cm depth from government sources, such as the following:
- India: Soil Health Card (SHC) data that includes SOC measurement at depths of 15 or 20 cm
- European Union: LUCAS (Land Use/Cover Area frame statistical Survey) Topsoil Survey data that includes SOC measurements at depths of 0–10 and 10–20 cm
- Ethiopia: EthioSIS (Ethiopia Soil Information System) data that includes SOC measurements at 0–20 cm
Projects may use data that does not meet the 30 cm depth requirement only for model calibration and validation under quantification approach 1, provided that the following conditions are met:
- The modeling outputs reflect SOC stock changes to a depth of at least 30 cm.
- The extrapolation method used to reach 30 cm is clearly and transparently described.
To be able to proceed with verification, projects must submit project-specific SOC measurements that fully comply with all VM0042 requirements, including depth, sampling protocols, and standards for quality control and quality assurance.