Understanding the Active Carbon Budget: A Study of Soil Inorganic Carbon in Southwestern Idaho

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Student Presentation

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Jennifer Pierce


Soil inorganic carbon (SIC) represents the third largest carbon pool within the active carbon cycle; however, there is much contention on whether fluxes into this pool are inextricably linked to the storage of atmospheric CO2. This study is investigating the total amount of carbon storage and whether or not this pool is being disturbed by irrigation practices.

We collected soil samples along terraces of the Boise River and along irrigated and adjacent undisturbed transects near Mountain Home (MH). We analyzed samples for their inorganic carbon content using pressurized calcimetry. Results show SIC storage as CaCO3 is significant, with an undisturbed storage density of 187 t/ha carbon (1 m depth).

In undisturbed transects (~ 1.5 m), average SIC is 2.2 wt. % compared to 1.5 wt. % in irrigated profiles. SIC in irrigated soils may be lower than in undisturbed profiles; however, peak carbonate amounts are deeper in irrigated transects. This could imply that in irrigated profiles, there is a downward movement of SIC due to the leaching of carbonates from increased water percolation during irrigation. A smaller peak in SIC at ~ 0.5 m in both irrigated and non-irrigated profiles may be CaCO3 precipitation associated with the rooting zone.

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