Applications of Streptomyces jingyangensis T. and Bacillus mucilaginosus A. improve soil health and mitigate the continuous cropping obstacles for Pinellia ternata (Thunb.) Breit

Soil microflora disorder has been regarded as one of the critical causes for the continuous cropping obstacles that result in stunted plant growth, serious disease incidence, and low yield and quality in crops. Pinellia ternata (Thunb.) Breit. is a traditional Chinese herb with important pharmacological values in its dried tuber. However, this plant is subject to the continuous cropping obstacles when growing in the same block of land for several years. In this study, both field and pot experiments were conducted to investigate the effects of Streptomyces jingyangensis T. and Bacillus mucilaginosus A. additions on the mitigation of continuous cropping obstacles for Pinellia ternata over 3 years. The tuber yield and quality were measured, and the soil enzymes and microflora structure examined. The results showed that the tuber yield of Pinellia ternata was increased by 40%− 68%, the plant morbidity reduced by 12%−67%, and the tuber quality improved under the two bacteria applications. High-throughput sequencing on soil samples revealed that, higher fungal richness and fungi: bacteria (F/B) ratio result in microflora disorder in the continuously cropped soil. The additions of Streptomyces jingyangensis and Bacillus mucilaginosus or fallowing decreased the fungal richness and the F/B ratio in the soil. Streptomyces jingyangensis addition converted the fungal community composition in the continuously cropped soil to a level that is similar to fallowed soil. The additions of the two bacteria selectively suppressed some soilborne pathogenic or harmful microbes such as Acremonium, Fusarium, and Acidobacteria genera, but promoted some beneficial microbes such as Lysobacter, Bacillus, and Chaetomiaceae genera, in ways that are different from fallowing. The activities of soil enzymes including urease, alkaline phosphatase, catalase and peroxidase were increased by the two bacteria additions. The results of this study suggest that the additions of beneficial bacteria can improve soil health and provide an effective tool to overcome the continuous cropping obstacles for Pinellia ternata.