Table 4 The characteristics of biochar before and after AD

pH

8.85

8.59

Electrical conductivity (mS cm⁻¹)

0.62

3.67

Ash (%)

19.64

12.57

C (%)

76.93

78.02

N (%)

0.52

0.96

Nitrate nitrogen (mg L⁻¹)

4.2

5.2

Ammonia nitrogen (mg L⁻¹)

16

184

P (%)

0.09

0.32

Ca (%)

1.22

1.10

Mg (%)

0.22

0.34

K (%)

0.47

0.74

Mn (%)

328.60 × 10^–4

246.09 × 10^–4

Zn (%)

73.74 × 10^–4

89.07 × 10^–4

Cu (%)

14.35 × 10^–4

13.95 × 10^–4

Fe (%)

0.34

0.31

Ni (%)

20.51 × 10^–4

31.48 × 10^–4

Co (%)

8.67 × 10^–4

10.85 × 10^–4