Applying an appropriate rate of rice husk biochar improves the microbial community structure of rhizosphere soil in continuously cropped sesame.

Although biochar can mitigate the incidence of sesame (Sesamum indicum L.) bacterial wilt under continuous cropping conditions, the underlying soil micro-ecological mechanisms remain unclear. Therefore, this study evaluated the diversity and structure of the rhizosphere microbial community under different biochar application rates (Y0 = 0; Y1 = 3.75; Y2 = 7.50; Y3 = 15.00; Y4 = 30.00; t ha-1) and health statuses (H = healthy and D = diseased) during the mature period of sesame under continuous cropping conditions using 16 S rDNA and ITS amplicon sequencing. The results indicated that the sesame yield under Y3 (15.00 t ha-1) increased by 6.29% compared with that of the control (Y0). Compared with that in Y3H, the relative abundance (RA) of Macrophomina in Y3D increased significantly, by 2.03 percentage points. Moderate biochar application reduced the relative abundance of Ralstonia and Macrophomina in diseased plants, with D having a greater RA than H did. The fungal species with notable differences in Y3H were g_Parasola; however, g_Alternaria was present in Y3D. Compared with those in Y3D, the RAs of p_Chloroflexota, o_Rhizobiales_A_504721, and g_Ohtaekwangia in Y3H increased by 0.850, 0.213, and 0.094 percentage points, respectively. However, those of the bacterial genera g_Nitrospira_C, g_Phenylobacteria, g_KBS296, and g_Sinomonas were opposite in Y3D. Overall, moderate biochar (15.00 t ha-1) was beneficial for the growth of continuously cropped sesame.