Wild-simulated ginseng (WSG, Panax ginseng C.A. Meyer) must be cultivated in mountainous forests without installation of artificial facilities or treatment of chemicals. Because cultivation of these medicinal plants requires a long-term period, soil properties and rhizobacteria are known as major factors affecting their growth. This study was aimed to investigate correlations of soil bacterial community with soil chemical properties and growth of 10-year-old WSG. Most of the growth characteristics of WSG were higher in southern region than in northern regions, while leaflet length and leaflet width of WSG were higher in northern regions. In all WSG cultivation sites, the most dominant phyla were Proteobacteria and Acidobacteria in the bacterial community. In Principal component analysis (PCA), soil bacterial community was affected by exchangeable cations (calcium, magnesium), soil pH, total nitrogen, cation exchange capacity, and organic matter. Soil pH was the most effective factor in this study because all studied sites were acidic soils. In spearman’s coefficient analysis, 9 of 13 growth characteristics of WSG showed significantly positive correlation with the relative abundance of Actinobacteria, while rhizome length and number of rootlets showed significant negative correlations with population of Acidobacteria. Therefore, growth characteristics of WSG in different cultivation sites can be affected by various soil environmental factors. These results can help foresters find suitable cultivation sites for WSG.

Soil properties are one of the major factors determining the growth of vegetation. These properties drive the selection of the dominant bacterial community profiles, which eventually determines the soil quality and fertility. The abundance of preferential bacterial community assists in better productivity of a particular type of vegetation. The increasing focus on the health and well-being of the human population has resulted in a shift in paradigm to concentrate on the cultivation of medicinal plants such as Wild-simulated ginseng (WSG). These plant species take a long time for their growth and are generally cultivated in the mountainous forest trenches of Far East countries like South Korea. This study was conducted to decipher the bacterial community profiles and their correlation with soil chemical properties, which would give a broader idea about the optimum growing conditions of such an important medicinal plant. The important edaphic factor determined in this study was the soil pH, which was recorded to be acidic in all the studied cultivation sites. In agreement with the edaphic factor, the relative abundance of Acidobacteria was found to be highest as this phylum prefers to grow in acidic soils. Moreover, the total organic matter, total nitrogen and cation exchange capacity were found to be significantly correlated with the bacterial community. Hence, these results will help to identify the suitable cultivation sites for WSG and increase the productivity of these medicinal plants.

Rice paddies are dynamic areas for microbe-mediated nitrogen cycling and this could be driven by the long-term alteration of paddy soil edaphic factors. The objective of this study is to evaluate the lasting impact of long-term compost fertilization on the soil chemical properties of paddy fields, determining the size of the microbial guilds involved in nitrification and denitrification. Soil sampling was done on paddy fields without fertilizer, with NPK + compost, and with compost application, and the soil chemical properties of the fields were determined from 2018 to 2021. The abundance of genes related to nitrogen cycling was measured using quantitative PCR (qPCR). Annual analyses showed that the studied soils have attained stable, baseline chemical properties with significantly increased phosphorus (P2O5), potassium (K), SOM, and total nitrogen (TN) due to decades of fertilization with NPK + compost and compost. Consequently, the genes related to bacterial amoA, nosZI, and nosZII were significantly increased in Com- and NPKCom-amended soils compared to the NF paddy field. The nirK gene abundance was unaffected after long-term amendment with compost. A positive correlation was found between the archaeal amoA gene abundance and DOC, while SOM and TN were consistently positively correlated with the abundances of bacterial amoA, nosZI, and nosZII genes, in addition to interactions with potassium and DOC. Principal component analysis (PCA) indicated soil variabilities across treatments, where the unfertilized paddy field contained lower SOM and nutrient contents with a characteristic nirK gene abundance. Similar variabilities in terms of the SOM, TN, K, nosZI, and nosZII gene abundances were observed in the Com and NPKCom paddy fields. Long-term amendment with NPK + compost and compost created soil paddy fields with stable soil chemical properties with higher SOM and nutrient contents, which established higher abundances of genes associated with denitrification and nitrification that were observed during the fallow period.

Wild-simulated ginseng (WSG, Panax ginseng C.A. Meyer) is the most important medicinal plant naturally cultivated in the forestry environment. The growth and active component content of WSG can be influenced by various environmental factors, such as climate conditions, physiognomy, soil properties, and soil bacterial structure. The aim of this study was to investigate the relationship between the growth characteristics of WSG and the soil bacterial community living in a rhizosphere environment. Experimental subjects were 7- and 13-year-old WSG cultivated in the central region (Yeongju) of Korea. The growth characteristics of WSG, divided into aerial parts, root parts, and weight parts, were measured. Rhizome length was significantly higher for 13-year-old WSG, while the number of rootlets was higher for 7-year-old WSG. As a result of analyzing the soil bacterial communities of WSG cultivation sites using next-generation sequencing (NGS), Proteobacteria and Holophagae were found to be the dominant species in the phylum level and class level, respectively. Rhizome length was positively correlated with Bacteroidetes at the phylum level, but it was negatively correlated with Thermoleophilia and Gemmatimonadetes at the class level. Pedospharae showed a negative correlation with the number of leaflets and petiole length, while Clostridia showed a positive correlation with the number of rootlets. The growth of WSG might vary depending on the environment in which it is cultivated. It is especially affected by soil properties and soil bacterial communities. Therefore, in future studies, it will be necessary to isolate and identify soil microorganisms living in WSG cultivation sites and then confirm their growth-promoting effects on WSG.

Organic fertilizer application in agricultural land is known to improve soil microbial processes, fertility, and yield. In particular, stable changes in soil chemical composition through multi-year fertilization of organic fertilizers are thought to cause changes in the microbial community. Here, the effects of oil cake amendments (OC) on soil bacterial diversity, community profile and enzyme activity were evaluated and compared to those amended with chemical fertilizer (NPK). The comparison of diversity indices between OC and NPK amended soils shows that application of oil cake has increased microbial diversity potentially with an increase in the number of different microbial groups. The ordination plot distinguished and clustered both treatments showing differential effects of soils chemical factors on the microbial communities of each treatment. Proteobacteria, Verrucomicrobia and Bacteriodetes were significantly abundant in OC amended soil than in the NPK received soil, indicating alterations in community structure, composition, and diversity con-current to the changes in pH, Ca and Mg contents of the soil. These shifts in bacterial community structure and composition could also be observed from the phylum to the genus level in both NPK and OC amended soils partially explained by differences in soil chemical factors. The OC soil compared to the NPK amended soil also contain significantly higher abundance of predicted genes corresponding to enzymes related to biogeochemical cycling, decomposition and plant growth promotion. Collectively, these results support the use of an unconventional organic fertilizer positively altering bacterial populations in jujube orchards. The application of oil cake-based organic fertilizer improved microbial diversity and enhanced potential ecosystem functions related to bio-geochemical cycles, mineralization and plant growth promotion.