An Automated Laboratory Method for Measuring CO2 Emissions from Soils

Core Ideas A GC method to measure soil CO2 emission was developed and compared with Solvita CO2 burst method. A strong exponential relationship between Solvita and GC method was observed. CO2 emissions from soils increased with drying temperature to a maximum at 65°C. The data presented highlight the narrow linear range of the Solvita method. The standardized procedure increased rate of analysis and reduced costs. A gas chromatography (GC) headspace method was developed for soil microbial respiration (CO2 emission) analysis after a 24‐h incubation of a rewetted soil. The GC method was compared with the Solvita CO2 burst method by analyzing 18 different soils that were air‐dried (22°C) or dried at 45, 65, and 105°C for 24 h before rewetting. A strong exponential relationship between the Solvita color number and GC headspace CO2–C emission was observed. Compared with air‐dried soils, drying at 65°C led to increased CO2 emission and reduced variation among sample replicates, while drying at 105°C led to a reduction in CO2 emission and an increase in variability. The GC method does not require sample dilution, provides data that is highly correlated to the Solvita method, and has a wider dynamic test range than the Solvita method. The developed GC method could be adapted to automation for commercial laboratory use.