|Plan precision target
|Avg sampling density
|6.5 acres / sample
|Minimum sample sites/stratum
Field-level plan details
Sample plan design techniques
Soil carbon stocks are estimated from measurements taken at sample sites. Determining how many samples to take is a balancing act. Too many and the project becomes expensive. Too few samples and the results have an unacceptable level of uncertainty.
Yard Stick solves this challenge with a process known as "stratified random sampling." Using published, peer-reviewed soil data from the United States Geological Survey, we estimate expected soil carbon values and then use data science to divide fields into areas of similar types of soil. These are known as "strata" (singular: “stratum”). Next, we calculate required number of samples based on your project’s budget and/or required precision. Lastly, we randomly place the required number of samples within each stratum. By taking random samples within a stratum, we can consider the samples as being representative of the stratum as a whole, and therefore a smaller number of samples are needed to achieve a target level of precision.
For more technical detail on our stratification techniques, click here, or select “Stratification methods doc” from the dropdown above.
Next steps to a baseline
- Require dry combustion (sometimes also called “total combustion”) for carbon analysis. Loss on ignition (“LOI”) is cheaper but not as accurate, and will not be accepted by the highest-quality soil carbon markets.
- Ensure samples will be treated to remove inorganic carbon (IC) before analysis for organic carbon (OC). Organic carbon is also sometimes called “Total Carbon,” but just be sure IC is removed first.
- Limit your search to labs with either NAPT or ALP accreditation.
- Confirm your lab will do bulk density analysis before soil carbon analysis.