Short-term releases of CO2 from newly mixed biochar and calcareous soil.

The work aims to quantify native organic C mobilized in one calcareous soil in the 21 days after addition of biochar at a range of high to very high doses. The experiment was carried out in unplanted microcosms and CO2 flux was used as a measure of net mineralization. A rapid methodological approach, which does not require 13C as a tracer, was used to assess any priming effects induced by the biochar. The amount of CO2-C mobilized was small relative to the amount of biochar C and proportional to the amount of the biochar added. The additional CO2–C was similar to the content of the WSOC of the biochar added in each respective dose. No interaction with native soil C, i.e. priming effect, was observed.