Using combustion analysis to simultaneously measure soil organic and inorganic carbon
Year: 2024
Type: article
Abstract: Soil organic carbon (SOC) and soil inorganic carbon (SIC) are of longstanding interest due to their relationship with other key soil properties and indications for soil health and carbon storage. At the USDA-NRCS Kellogg Soil Survey Laboratory (KSSL), total carbon (SOC + SIC) is determined via dry combustion analysis, while calcium carbonate (CaCO3) equivalent is determined via manocalcimetry. For calcareous (carbonate bearing) samples, SIC is estimated as 12% of CaCO3 equivalent, while SOC is estimated as the difference between measured total carbon and estimated SIC. An alternative dry combustion method for the measurement of SOC and SIC pools was evaluated with the goal of directly measuring – not estimating – inorganic and organic carbon on calcareous samples. The alternative dry combustion method comprises two variants that differ in temperature-ramps and carrier gases used. Both variants were applied in duplicate to 110 diverse samples, including 32 calcareous samples, from across the USA that had been previously characterized by the KSSL. Samples were selected to capture wide variability in carbon contents. Comparing carbon data outcomes with data from the legacy KSSL methods revealed one method variant as best for calcareous samples, whereas the other variant was preferred for non-calcareous samples. A combination of the two method variants offers an accurate and direct measurement of SOC and SIC. For calcareous samples, mid-infrared (MIR) spectral analysis demonstrated the new method as slightly more accurate than legacy KSSL methods for estimating SOC and SIC.
Source: Geoderma
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $2,990
OpenAlex ID: W4403709482