A soil fumigant increases American ginseng ( Panax quinquefolius L.) survival and growth under continuous cropping by affecting soil microbiome assembly: a 4-year in situ field experiment

Abstract

ABSTRACT The replant problem is a widespread challenge in agricultural production and results in significant financial losses. The survival and development of American ginseng ( Panax quinquefolius L.), a well-known perennial medicinal plant, also typically suffer from replant problems. At present, efficient strategies for this issue and the underlying mechanisms are still lacking. Here, a series of in situ field experiments over a 4-year period were conducted to investigate the effectiveness and possible mechanisms of soil fumigation and fungicide in improving American ginseng survival under continuous cropping. During the 4-year ginseng cultivation, the seedling emergence rates in the dazomet fumigation-treated group (DF) decreased from 90.67% to 52.92%, from 78.67% to 0% in the lime sulfur fungicide-treated group (LS), and from 66.67% to 0% in the control. The fresh root weight in DF increased from 0.36 to 28.72 g, from 0.32 to 13.74 g in LS, and from 0.42 to 9.06 g in the control for the first 2 years. However, no ginseng survived during the following 2 years. Moreover, DF significantly decreased root rot disease incidence by 55.55% compared to LS-treated soil and 69.39% compared to non-treated soil. The correlation analysis results showed that both diversity and structure indices of bacteria and fungi were significantly correlated with root biomass and disease incidence in the second year. In summary, DF has presented a significant beneficial effect on American ginseng development. Additionally, the second year is the critical period to shape the soil microbial community, which could have a long-lasting effect on the development of American ginseng. IMPORTANCE Numerous reports of soil fumigants and fungicides on annual crops exist; however, it is unclear whether the single application to perennial plants persistently improves plant growth and controls disease or whether it has a long-lasting impact on soil microbes. We found that soil fumigation enhances ginseng growth and suppresses root rot disease by reshaping the soil microbial community. Our findings benefit the agricultural development of ginseng and provide a theoretical basis for the prevention of ginseng diseases.