4.2. Effects of biochar aging process and incubation condition on soil
acidity
Differences in pH trends and exchangeable properties were
observed between treatments in which PB and PBa were added.
First, the pH values of PBA were lower than those of PBV and PBS
throughout the incubation period, although the initial pH value of
PBa was higher than that of PB. A similar trend was shown by the
soil exchangeable properties (Table 4). This result suggests that
biochar PB could effectively amend soil acidity, but the effectiveness
decreased when biochar had undergone short-term aging.
The difference in effects was caused by the combination of the
following factors: (a) carbonate contents in PB were higher than in
PBa (see Section 3.1.2); (b) more abundant soluble and exchangeable
base cations were found in PB than in PBa (Table 2); (c) more
regular porosity and higher levels of surface area were observed in
PB than in PBa (Table 2 and Fig. 1), such that more soil
exchangeable base cations could be immobilized in PB treatments
resulting in the relative increase in CEC (PBV and PBS vs. PBA,
P