Effect of vermicompost application on root growth and ginsenoside content of Panax ginseng

Vermicomposts are valuable by-products of organic wastes and can be used to improve soil environments in ginseng production. We compared the effects of food waste vermicompost (FWV), cow manure vermicompost (CMV) and paper sludge vermicompost (PSV) on several ginseng root production variables. Interactions between soil chemical properties, root growth, ginsenoside content and plant mineral content were also investigated. In the PSV treatment, the root yield increased by 40 t ha(-1) compared to the untreated control. Nitrate concentration correlated negatively with root yield, and none of the vermicompost treatments differed significantly from the control in terms of root loss. Soil pH correlated positively with root weight, and total ginsenoside content did not vary among treatments, although some individual ginsenosides did differ among treatments. Root iron content correlated strongly with total ginsenoside content, and total ginsenoside content correlated negatively with root yield. Overall, our results showed that the root yield increase was not due to nutrient increase. Vermicompost was safe to use in relation to root rot disease, and it favourably elevated the pH of fields converted from rice paddies to ginseng production. Ginsenoside was not involved in defence mechanisms against root rot disease. Root iron content may have been involved in the metabolism of ginsenoside, and there was an apparent trade-off between ginsenoside content and root yield. Finally, vermicompost application altered resource allocation and soil chemical properties, which led to novel interactions between root parameters and components.