Gypsum effects on plant growth, nutrients, ginsenosides, and their relationship in American ginseng

Abstract

Wild American ginseng is typically found in the shade of deciduous forests, in slightly acidic soils with a relatively high Ca content. Wood-cultivated ginseng is often grown using forest farming agroforestry systems under similar conditions. Supplementing Ca by soil incorporation of gypsum (CaSO4·2H2O) is often recommended for wood-cultivated ginseng. The objective of this study was to determine the effects of gypsum application on ginseng growth, tissue nutrients, and ginsenoside contents in American ginseng. Three-year-old rootlets were grown for 120 days with 0, 2, 4, 8, or 16 Mt·ha−1 gypsum in greenhouse containers. Gypsum application reduced the soil pH slightly and elevated soil electrical conductivity (EC) and available soil Ca and S contents. While the Ca content in the ginseng increased with increasing levels of applied gypsum, shoot and root growth decreased. Root fresh weight prior to transplanting primarily affected the contents of ginsenoside Re, Rb1, Rc, and Rd and total ginsenosides. Gypsum treatment increased ginsenoside Rb1, Rc, and Rd and total ginsenoside contents. Furthermore, soil Ca, Mn, Cu, and Al contents positively correlated with total ginsenoside, but Mg was negatively correlated. HPLC analysis of root ginsenosides revealed that, although the concentrations of ginsenoside Rb1, Rc, and Rd increased with gypsum treatment, the contents of total ginsenosides were reduced. Changes in concentration may result from reduced root growth. Therefore, the results suggest that excess gypsum application (over 2 Mt·ha−1) is not beneficial for American ginseng production due to reduced plant growth.