The Combination of Biochar and Bacillus subtilis Biological Agent Reduced the Relative Abundance of Pathogenic Bacteria in the Rhizosphere Soil of Panax notoginseng .

In the continuous cropping of Panax notoginseng , the pathogenic fungi in the rhizosphere soil increased and infected the roots of Panax notoginseng , resulting in a decrease in yield. This is an urgent problem that needs to be solved in order to effectively overcome the obstacles associated with the continuous cropping of Panax notoginseng . Previous studies have shown that Bacillus subtilis inhibits pathogenic fungi in the rhizosphere of Panax notoginseng , but the inhibitory effect was not stable. Therefore, we hope to introduce biochar to help Bacillus subtilis colonize in soil. In the experiment, fields planted with Panax notoginseng for 5 years were renovated, and biochar was mixed in at the same time. The applied amount of biochar was set to four levels (B0, 10 kg·hm-2 ; B1, 80 kg·hm-2 ; B2, 110 kg·hm-2 ; B3, 140 kg·hm-2 ), and Bacillus subtilis biological agent was set to three levels (C1, 10 kg·hm-2 ; C2, 15 kg·hm-2 ; C3, 25 kg·hm-2 ). The full combination experiment and a blank control group (CK) were used. The experimental results show that the overall Ascomycota decreased by 0.86%~65.68% at the phylum level. Basidiomycota increased by -73.81%~138.47%, and Mortierellomycota increased by -51.27%~403.20%. At the genus level, Mortierella increased by -10.29%~855.44%, Fusarium decreased by 35.02%~86.79%, and Ilyonectria increased by -93.60%~680.62%. Fusarium mainly causes acute bacterial wilt root rot, while Ilyonectria mainly causes yellow rot. Under different treatments, the Shannon index increased by -6.77%~62.18%, the Chao1 index increased by -12.07%~95.77%, the Simpson index increased by -7.31%~14.98%, and the ACE index increased by -11.75%~96.12%. The good_coverage indices were all above 0.99. The results of a random forest analysis indicated that Ilyonectria , Pyrenochaeta , and Xenopolyscytalum were the top three most important species in the soil, with MeanDecreaseGini values of 2.70, 2.50, and 2.45, respectively. Fusarium , the primary pathogen of Panax notoginseng , ranked fifth, and its MeanDecreaseGini value was 2.28. The experimental results showed that the B2C2 treatment had the best inhibitory effect on Fusarium , and the relative abundance of Fusarium in Panax notoginseng rhizosphere soil decreased by 86.79% under B2C2 treatment; the B1C2 treatment had the best inhibitory effect on Ilyonectria , and the relative abundance of Ilyonectria in the Panax notoginseng rhizosphere soil decreased by 93.60% under B1C2 treatment. Therefore, if we want to improve the soil with acute Ralstonia solanacearum root rot, we should use the B2C2 treatment to improve the soil environment; if we want to improve the soil with yellow rot disease, we should use the B1C2 treatment to improve the soil environment.