Background: Crop rotation plays an important role in improving soil chemical properties, minimizing the presence of disease pathogens, and assists in neutralizing autotoxic effects associated with allelochemicals. Methods and Results: Five rotation crops of sudan grass, soybean, peanut, sweet potato, and perilla were cultivated for one year with an aim to reduce yield losses caused by repeated cropping of ginseng. In 2-year-old ginseng grown in the same soil as a previous ginseng crop, stem length and leaf area were reduced by 30%, and root weight per plant was reduced by 56%. Crop rotation resulted in a significant decrease in electrical conductivity, NO3, and P2O5 content of the soil, whereas organic matter, Ca, Mg, Fe, Cu, and Zn content remained-unchanged. Soil K content was increased following crop rotation with sudan grass and peanut only. Rotation with all alternate crops increased subsequent ginseng aerial plant biomass, whereas root weight per plant significantly increased following crop rotation with perilla only. A significant positive correlation was observed between root rot ration and soil K content, and a significant negative correlation was observed between ginseng root yield and the abundance of actinomycetes. Crop rotation affected the soil microbial community by increasing gram negative microbes, the ratio of aerobic microbes, and total microbial biomass whereas decreases were observed in actinomycetes and the ration of saturated fatty acids. Conclusions: In soil exhibiting crop failure following replanting, crop rotation for one year promoted both soil microbial activity and subsequent ginseng aerial plant biomass, but did not ameliorate the occurrence of root rot disease.

To study the effect of crop rotation on the control of ginseng root rot, growth characteristics and root rot ratioof 2-year-old ginseng was investigated after the crops of 18 species were cultured for one year in soil contaminated by thepathogen of root rot. Fusarium solani and Cylindrocarpon destructans were detected by 53.2% and 37.7%, respectively, frominfected root of 4-year-old ginseng cultivated in soil occurring the injury by continuous cropping. Content of NO3, Na, andP2O5 were distinctly changed, while content of pH, Ca, and Mg were slightly changed when whole plant of crops cultured forone year were buried in the ground. All of EC, NO3, P2O5, and K were distinctly increased in soil cultured sudangrass, pea-nut, soybean, sunnhemp, and pepper. All of EC, NO3, P2O5, and K among inorganic component showed negative effect onthe growth of ginseng when they were excessively applied on soil. The growth of ginseng was promoted in soil cultivatedperilla, sweet potato, sudangrass, and welsh onion, while suppressed in Hwanggi (Astragalus mongholicus), Deodeok(Codonopsis lanceolata) Doraji (Platycodon grandiflorum), Gamcho (Glycyrrhiza uralensis), Soybean. All of chicory, lettuce,radish, sunnhemp, and welsh onion had effective on the inhibition of ginseng root rot, while legume such as soybean,Hwanggi, Gamcho, peanut promoted the incidence of root rot. Though there were no significant correlation, NO3 showedpositive correlation, and Na showed negative correlation with the incidence of root rot.