## 4 Discussion  
That Biochar can promote crop growth and performance when added to soil has been previously reported for crops such as soybean [8], maize [1], and cabbage [19]. It has also been known that soil microbes can promote plant growth by soil amendment [20]. However, there was less information about the impact of the interaction between biochar and microbes on plant production [21]. Thus, biochar was applied together with microbes in the soil planted with Chinese cabbage. In the present study, we found that the interaction of biochar with microbes promoted cabbage growth stronger than biochar or microbes alone, presumably that the biochar interaction with microbes in soil could enhance crop growth and performance. These outcomes confirmed previous findings that indicated the positive effects of biochar-microbe interactions after the combination of biochar and microbe application in soil on the growth, yield, and nutrient availability of different plant species such as soybean [8], sunflower [22], and rice [23]. The improved examined growth parameters as a result of biochar-microbe interactions might be ascribed to the role of biochar in microbial growth and activity in soil stimulation in general [24]. It is well known that soil microbes are an important soil component of ecosystems, playing an important role in soil organism transformations, the maintenance of soil fertility, and plant material conversions [4]. Soil microbes are active contents that can improve soil fertility by impacting on the microbial community structure in rhizosphere soil and its nutrient cycling [25]. Previous studies suggested that soil microbial biomass could be increased in soil supplemented with biochar and that the microbial community structure and abundance were changed over time [26]. Both soil microbes, _Chlorbatchrum_ sp. ACCC10085 and _B. mucilaginousus_ AS1.153, were applied in the soil with the addition of biochar in the present study. The microbial content in the rhizosphere soil was higher when biochar was added. Biochar has a porous structure and the ability to change soil porosity [27], which might have created a better environment for soil microbes to grow and reproduce. Considering that these two microbes have an ability to solubilise phosphorus and potassium, it was presumed that the interaction of biochar with the microbes could improve the soil fertility by enhancing microbial activity [13]. The impact of biochar on soil microbes is diverse. Many studies provided different hypotheses to explain the effect of biochar application on soil microbe growth and activity. [PERSON] et al. [28] and [PERSON] et al. [29] reported that biochar may increase the soil bacteria amount by improving the soil's pH. [PERSON] et al. [9] concluded that the high cation exchange capacity and adsorption capacity of biochar helped to maintain nutrients in the soil and provide substrates for the growth and metabolism of soil microbes. [PERSON] et al. [7] found a high root colonisation level of arbuscular mycorrhizal fungi as a result of biochar application. In addition, the biochar indirectly affected the growth and metabolic activity of soil microbes by altering the soil properties, regulating nutrient availability, and regulat  
\begin{table} \begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Indexes b**} & **icrobial** & **The Relative Abundance of** & **The Relative Abundance of** \\  & **Content** & _Orthobactrum_ & _Bacillus mucilaginousus_ \\ \hline OM & 0.952 * & 0.987 * & 0.657 \\ AP & 0.987 * & 0.991 ** & 0.501 \\ AK & 0.657 & 0.664 & 0.959 * \\ PS & 0.998 ** & 0.977 * & 0.636 \\ US & 0.975 * & 0.976 * & 0.494 \\ FW & 0.958 * & 0.973 * & 0.820 \\ PC & 0.970 * & 0.990 ** & 0.755 \\ KC & 0.945 & 0.984 * & 0.965 * \\ \hline \hline \end{tabular}   
* **: *ing enzyme activity [30]. Overall, our results demonstrate the potential role of biochar application in improving soil microbe growth and reproduction in soil. However, adding excessive biochar to the soil can also have an inhibitory effect on soil microbes (Figure 2).