*3.2. Soil Cd Fraction and Growth Exhibition*

Even through the BC treatment raised the soil pH in comparison with CK, the soil Cd fractions only slightly changed except for those of the lettuce. Regardless of treatments and crops, F-I was the primary fraction of Cd in the soils, and accounted for 37–65% of the total concentration in general (Table 1). In comparison with CK, the BC treatment significantly (*p* < 0.05) changed the Cd in F-I and F-II of lettuce. For LSS treated with BC, the Cd proportion of F-I significantly (*p* < 0.05) increased, but F-II significantly (*p* < 0.05) decreased compared with CK. For LSC treated with BC and in contrast with CK, however, the Cd in the F-I significantly (*p* < 0.05) decreased and F-II significantly (*p* < 0.05) increased. The BC treatment did not significantly change the Ni proportion in the different fractions (detailed data not shown). F-IV was the primary fraction of Ni in general and accounted for 57–63% of the total Ni in the soils. Besides sequence extraction, 0.1 N HCl and 0.05 N EDTA were used to extract the available concentration of Cd and Ni in the soils. Approximately 58–68% and 56–69% of the total Cd in the soils could be extracted by 0.1 N HCl and 0.05 N EDTA, respectively. Because most of the Ni was presented in the F-IV fraction, 0.1 N HCl and 0.05 N EDTA only extracted 10–15% and 9–13% of the total Ni in the soils, respectively. In comparison with CK, the BC treatment did not significantly decrease the two chemical agents' extractable Cd and Ni concentrations in the soils in general.

Compared to CK treatments, the root length, shoot height, shoot fresh weight, and SPAD reading increased under BC treatment in general (Table 2). However, most of the differences were not statistically significant. These results revealed that BC treatment promoted the growth of PCC in general.


**Table 2.** The growth exhibitions (mean ± standard deviation) of pak-choi and lettuce grown in the contaminated soils amended with or without applying husk biochar 1.

<sup>1</sup> The same lowercase letter indicates no significant difference between treatments for the same leafy vegetable and the same growth exhibition. <sup>2</sup> The meanings of abbreviations are the same as in Table 1. <sup>3</sup> SPAD reading: soil plant analyzer development reading.
