In general, the promotion or suppre

In general, the promotion or suppression of abiotic CO2 release was a
short-term effect and determined by the amount of carbonates of biochar,
where pH took effect through interaction between biochar and
soil. Murray et al. (2015) compared the stability of low- and high-ash
biochars, and found more CO2 released from Ferralsol (acidic soil) in
the first day after applying tomato-biochar and blue-mallee-biochar.
The results suggested a higher abiotic release and less stable structure
of low-ash tomato-biochar in acidic soils (Murray et al., 2015). In this
study, biochar was made rice straw and had a relative lower ash content
and less stable carbon structure, which tended to promote more CO2
than biochar made from other feedstocks. The IC/TC ratio decreased
during the incubation, accompanied with the equilibrium of pH in the
soil-biochar mixture. Furthermore, after subtracting the abiotic CO2 release,
the CO2 release from organic carbon mineralization still showed
the same trend as the total carbon release. Therefore, dissociation of carbonates
was not the only way responsible for the increase of the observed
CO2 emission. Other mechanism such as organic carbon
mineralization by microbial communities also contributed to the
phenomenon