The carbon stocks in the top 30cm of soil is calculated using a recorded bulk density (0-30cm) in g/cm³, and % soil organic carbon (0-30cm). Both of these metrics require soil samples (cores) to be sent to a lab for analysis.

Once you’ve added your data for bulk density and soil organic carbon, you can view your results in the Carbon Stocks Report, which shows the total carbon stored in each of your blocks in tonnes, as well the tonnes per hectare (based on averages from your recorded results).

Soil carbon is most changeable in the top 10cm of soil, but measuring up to 30cm accounts for fluctuation of carbon levels at different soil depths, and better explains changes under different farm management. Including bulk density monitoring in the calculation of carbon stocks adjusts for changes in soil mass at different depths.

When monitoring this metric over time, we recommend taking your soil cores at approximately the same time each year, as soil carbon is known to vary seasonally.

Soil organic carbon % testing

1. Collect a 30cm soil core at your sample location.

2. Repeat the collection of a 30cm depth soil core at up to 20 sample sites to take into account the variability of your soils – you can do this along a transect from your sample site. These cores can be mixed into one sample to send for analysis.

3. Send your soil samples for analysis, letting the lab know that the cores were taken at a 30cm depth.

Bulk density testing

1. Collect a soil core up to 30cm at your sample location. N.B. Once the corer is inserted to 30cm, the core you collect may have condensed to be less than 30cm, but do not try and go deeper. The condensed soil is part of the individual bulk density reading.

2. Send your soil samples for analysis, letting the lab know that the cores were taken at a 30cm depth.