Fundamentals
Bulk density
Soil mass per unit volume, used to convert carbon concentration into a stock per hectare.
Laboratory analysis reports carbon as a concentration. Turning that into tonnes per hectare requires bulk density, measured with a core of known volume.
Compaction, tillage and depth all change bulk density, so comparing stocks across dates or practices without accounting for it produces false gains or losses. Fixed-depth sampling plus measured density is the safe approach.
Frequently asked questions
Can default bulk density be used?
Only as a fallback. Management changes density, and defaults can shift a stock estimate materially.
What is equivalent soil mass?
An approach that compares stocks per unit mass rather than per fixed depth, correcting for density change.