Changes over the Years in Soil Chemical Properties Associated with the Cultivation of Ginseng ( Panax ginseng Meyer) on Andosol Soil

The sowing-to-harvest period for the medicinal plant Ginseng ( Panax ginseng Meyer) is 4–6 years. Although one of the primary soils used to cultivate ginseng in Japan is Andosol, there have been few studies of the changes in the soil’s chemical properties during the cultivation of ginseng in Andosol soil. Here, we investigated the chemical properties of Andosol soil by collecting soil samples from cultivation sites with various numbers of years of ginseng cultivation. A significant negative correlation was observed between the years of cultivation and the soil’s pH, indicating that soil acidification increased with an increasing number of years of cultivation. Similarly, exchangeable calcium (Ca) showed a significant negative correlation with the years of cultivation. The soluble aluminum (Al) concentration showed a significant positive correlation with the years of cultivation and was significantly negatively correlated with the exchangeable Ca and magnesium (Mg) contents. These results suggest that a decrease in pH due to Ca absorption by ginseng, increasing Al dissolution, and a further accelerated decrease in pH occur during the cultivation of ginseng in Andosols. The increase in soluble Al with increasing years of cultivation also affected the dynamics of essential trace elements in the soil, showing significant negative correlations with the soil’s soluble copper (Cu) and zinc (Zn) contents, indicating that the Cu and Zn contents decreased with increasing Al. Our findings indicate that in the cultivation of ginseng on Andosol soil, the soil’s soluble Al content is an essential factor in changes in the soil’s chemical properties.