Abstract:

Due to its high medicinal value, Astragalus membranaceus has been dug intensively and unrestrainedly in recent years, resulting in the near exhaustion of the resources. Exploring the suitable growth soil of Astragalus membranaceus could provide a theoretical basis for its artificial cultivation. In this study, the soil planted with Astragalus membranaceus for many years in Jiagedaqi City was taken as the research object. Morphological characteristics and soil nutrients of the typical soil profiles were analyzed. The results showed that the structures of surface soil were loose, the porosities were large and the colors were darker, which were dark brown in dry state and black in wet state. The deposition and parent material layers were solid, the porosities were small, and the soil colors gradually turned to yellow and brown with the increase of soil depth. The surface soil was fertile, with mainly loam textures and high organic matter contents, which were 122.07 and 110.09 g/kg, respectively. Organic matter contents in surface layer accounted for 52.0% and 82% of total organic matter content in the soil profile, respectively. Organic matter contents in the soil profiles showed a dramatic drop trend with the increase of soil depth. Total nitrogen contents in the surface layer were relatively high, which were 6.58 and 8.87 g/kg, respectively, but total phosphorus contents of the soil were relatively low, which were 0.07 and 1.01 g/kg, respectively, in the surface layers. The pH of the soil was between 5.11 and 6.35. The soil suitable for Astragalus membranaceus growth was with loose textures, frosty temperature condition, wet moisture condition and fertile, and with high soil organic matter contents, high total nitrogen contents, but low total phosphorus contents in the surface soil, and the pH value was weak acidity to neutrality.

Key words: dark brown soil, soil profile, soil chemical properties, Astragalus membranaceus, morphological description