Background Biochar is mainly used to enhance soil fertility, microbial activity, improve plant performance and reduce disease incidence. Methods A greenhouse experiment was designed to investigate the response of biochar on rhizosphere soil chemical properties, enzyme activity, microbial communities, and sugarcane Pokkah boeng disease (PB). Two sugarcane varieties Zhongzhe 9 (Z9) and ROC22, susceptible/resistant to PB, were cultivated and treated with: no biochar, 15 t ha(-1) biochar, and 30 t ha-1 biochar. Results The amendment of 30 t ha(-1 )of biochar (B2) significantly improve soil pH by 1.50% and 9.61% compared with that of B1 and B0, followed by 0.51% increase by 15 t ha(-1 )of biochar (B1) compared with that of control (B0). The application of 15 t ha-1 biochar significantly increased available phosphorus (AP) and ammonium nitrogen (NH4+-N) by 209.93 mg kg(-1) and 12.1 mg kg(-1), while the application of 30 t ha(-1) of biochar significantly increased 241.04 mg kg(-1) of available potassium (AK) (P < 0.05). Furthermore, biochar application increased the activities of soil acid phosphatase (S-ACP), urease (S-UE), and sucrase (S-SC). Alpha diversity analysis showed that the addition of biochar significantly altered the variety and abundance of rhizosphere microorganisms (P < 0.01) and increased the relative abundance of beneficial microorganisms Rhodanobacteraceae, Stachybotryaceae, Agaricacea, Talaromyces, Nectriaceae, Sistotrema, and Bacillus (P < 0.01). There was a significant decrease in the relative abundance of the soil pathogen Fusarium (P < 0.01). Conclusion These findings suggested that the application of 15 t ha(-1) biochar could bring desirable variations in soil functionalities, modulate soil microbial community by increasing soil health and reduce the disease index of PB.
