During the incubation duration, consistent bulk density (Bd)
about 1.10 Mg m−3 was found for the amended soils; however,
rapid increase of Bd was found in the control at 21 d and then
maintained a consistent value at about 1.40 Mg m−3 to the end of
the incubation (Fig. 2e). After incubation of 105 d, the Bd of the
biochar-amended soils significantly decreased from 1.42 Mg m−3 to
b1.15 Mg m−3, and rate of decease increased with the biochar application
rate (Table 2). Other than changes in the Bd, the biochar-amended
soils exhibited significantly higher total porosities (N50%) than the
unamended controls (41%) after 105 d incubation (Table 2). Fig. 2f
further shows a variation of porosity during the incubation duration;
the control and 2.5% biochar-amended soil presented unobvious
changes throughout the duration, and a gradual decrease in porosity
appeared in the 5% biochar-amended soil.