Abstract: In order to explore the best season to transplant Astragalus membranaceus var. mongholicus seedlings, a transplant contrast experiment was conducted in early-winter and spring season. During the experiment, the soil moisture, growth and development indicators as well as yield and quality of medical roots for the plant were measured accordingly. The result showed that compared with the spring-transplanted field, the soil moisture of 0-20 cm layer in the early-winter transplanted field was significantly higher during re-green stage of the seedlings but lower significantly during the growth evening stage of the adult plants in over 40 cm deep layer of soil; the re-green and bloom stage were ahead of 10 d and 13 d, respectively; the emergence power, re-green rate and emergence index increased by 32.65%, 4.4% and 0.2497, respectively, resulting in prolongation in growth stage and setting up good foundation for the medical root growth and accumulation in active component. Finally, there were 201,087 and 181,250 merchandised medical roots per hectare in the early-winter and spring transplanted fields respectively, resulting in 24.02% and 19.69% of the first-class medical roots, 5 400 kg·hm^-2 and 5 057 kg·hm^-2 of the medical fresh root yield, 0.121% and 0.098% of Astragaloside A, 0.080% and 0.052% of calycosin-7-glucoside content, 27.62% and 25.54% of water-soluble extract content, respectively. All above suggests that the early-winter transplant is more significant in cultivation effect for the plant, suggesting that the early-winter transplant cultivation should be advocated in the standardization production of the medical plant.

Key words: Astragalus membranaceus var. mongholicus, transplantation time, medical root yield, medical root quality