Abstract: In Platycodon grandiflorum production, continuous cropping results in a considerable reduction of crop yield. In order to find out the proper crop rotation of P. grandiflorum, aqueous extracts of different Concentrations of P. grandiflorum were prepared. The effect of those extracts on soybean’, wheat’ and radish’ seed germination and seedling growth were studied. The germination index (germination rate, germination potential, germination index, relative vigor index), growth index (seedling height, root length) and biomass (shoot and root fresh weight) were measured. The results showed that the effect of two kinds of extracts on the three kinds of seeds showed the inhibition of low concentration, the promotion of high concentration. Root extract effect is stronger than shoot extracts. The responses of three seedlings roots' on the two extracts were more sensitive than the shoots'. The comprehensive effect indexes of the three crops indicated that radish is more suitable to the P. grandiflorum rotation cropping.

Key words: Platycodon grandiflorum, Wheat, Radish, Soybean, aquatic extract