Abstract: Andrographis paniculata(Burm. F.) Nees has many functions, including antibacterial, anti-inflammatory, and antiviral. However, the continuous cropping obstacles in planting and production have adverse effects on the yield and quality of A. paniculata. In this study, a field experiment was conducted with two levels of bamboo charcoal addition \[1.2 kg·m^-2 (C1) and 2.4 kg·m^-2 (C2)\] in continuous cropping systems of A. paniculata for five years, with no bamboo charcoal addition as the control (C0). The agronomic traits were measured during the picking period, and the rhizosphere bacterial community structure, abundance, and diversity were examined using the Illumina Miseq high-throughput sequencing methods. The results showed that the application of bamboo charcoal was beneficial to the growth of A. paniculata in continuous cropping soil, with plant height, root length, stem thickness, chlorophyll content, fresh weight per plant, and andrographolide and dehydrated andrographolide contents being significantly higher than those without bamboo charcoal. Moreover, the promotion effect of high-level application of bamboo charcoal on the growth of A. paniculata was greater than that of low-level application. The application of bamboo charcoal increased bacterial diversity in the rhizosphere soil of the continuous cropping of A. paniculata, altered bacterial community structure, and increased the abundance of bacteria (Nitrospira, Bradyrhizobium) that are beneficial to nitrogen uptake. UPGMA clustering and PCoA β-diversity analysis showed that the composition of soil bacterial community was closely related to the level of bamboo charcoal application. In addition, RDA analysis showed that the abundance of three genera (Nitrospira, Bradyrhizobium and Candidatus_Solibacter) in the rhizosphere of A. paniculata was significantly positively correlated with many growth indices. The functional prediction of Tax4Fun showed that the application of bamboo charcoal could promote the upregulation of metabolicsrelated genes of soil bacteria and amino acid metabolism, nucleotide metabolism, and secondary metabolites. The application of bamboo charcoal in field cultivation of A. paniculata can improve its agronomic characteristics and promote the accumulation of active ingredients, and affect soil bacterial community structure and abundance, which facilitates the growth of beneficial bacterial populations and may play an important role in alleviating the continuous cropping obstacles of A. paniculata.

Key words: bamboo charcoal, Andrographis paniculata, continuous cropping obstacle, microbial diversity, high-throughput sequencing.