Inorganic Carbon (Calcite and Dolomite) Determination Using the Modified Pressure‐Calcimeter Method

ABSTRACT Soil inorganic carbon (SIC) quantification is critical for accurately determining soil organic carbon (SOC) in carbonate‐containing soils when SOC is determined as the difference between total C and SIC. Generally, the pressure‐calcimeter method (described by Sherrod et al.) is used to quantify SIC content using a relatively simple approach, with the method broadly used in laboratories globally to quantify SIC. The original study suggested using a 6 h incubation time based only on calcite (CaCO 3 ); dolomite (CaMg(CO 3 ) 2 )‐containing soils were neglected. Additionally, most laboratories adopting the pressure‐calcimeter method for SIC measurements shorten the incubation duration to 2 h to facilitate analytical efficiency. This study evaluated the optimal incubation time (from 2 to 48 h) for calcite and/or dolomite‐containing soils using the pressure‐calcimeter method as compared to the Chittick apparatus. Results identified 6 h as the optimal reaction time for maximum CO 2 release from dolomitic soils. Among 18 soils containing varying concentrations of calcite and dolomite, the pressure‐calcimeter and Chittick apparatus methods were strongly correlated ( R 2 = 0.98), supporting the accuracy of the pressure‐calcimeter method in quantifying total SIC content. Compared to traditional methods, the pressure‐calcimeter method offers enhanced safety, efficiency, and scalability for large‐scale soil analysis globally, and will capture all SIC within a 6‐h timeframe.