Biochar has positive effects as a soil acidity amendment which is a global concern. However, few studies
have been reported on the effect of aged biochar on soil acidity. Incubation methods with different
ventilation conditions may induce different effects on soil acidity amendment using biochar. This study
analyzed the effects of fresh and aged biochars on soil acidity amendment with different incubation
methods. Samples of typical acidic soil (plinthudults) and fresh Pinus massoniana bark were collected
from the hilly red soil region of southern China and used to create biochar (PB) with the oxygen-limited
pyrolysis method at 450 C. A 4-month-aged PB (PBa) which was produced by a natural forest fire was
collected from the same area as that of biochar PB. A 69 days incubation experimentwas conducted using
an improved incubation method. The treatments comprised 100 g soil + 2 g PBa (PBA), 100 g soil + 2 g PB
(ventilated incubation, PBV), 100 g soil + 2 g PB (sealed incubation, PBS) and 100 g soil only incubated
under ventilated (CKV) and sealed (CKS) conditions. Soil pH was measured periodically. Soil
exchangeable base cations, exchangeable acidity, exchangeable aluminum (Al3+) and cation exchange
capacity (CEC) were measured after incubation. Throughout the incubation period, PB and PBa positively
enhanced soil pH (P 0.05) between values in PBV and PBS. PB addition improved soil exchangeable base
cations and base saturation compared to PBa addition. Soil CEC levels in PBA, PBV, and PBS were not
significantly different from those in CKV and CKS, but CEC in PBV and PBS were significantly higher than
the CEC in PBA. All parameters in PBVwere not significantly different from the parameters in PBS. Biochar
PB can be used to amend soil acidity, but the efficiency declines to a certain extent if biochar PB has
undergone a short-term aging before being added to soils. The different ventilation conditions had little
influence on soil acidity amendment using biochar.