Cultivation Practices for Astragalus membranaceus in the Southeastern United States

Abstract

Astragalus membranaceus is a traditional Chinese medicinal herb and has been used for thousands of years. Information on its cultivation in Southeastern United States is lacking. In September 2006, three field experiments were planted in beds to test the effects of (1) deep tillage (subsoiling vs no subsoiling), (2) variety trial (seven variety from difference area), and (3) P (0, 29, and 58 kg ha-1) and K (0, 56, and 112 kg ha-1) fertilizer and lime on growth, root development, and astragaloside IV concentration in Auburn, Alabama on a Plinthic Kanhapludults soil. The fertility study was a 3 × 3 factorial augmented with a no-lime treatment at 29 kg P ha-1 + 56 kg K ha-1. Plant mortality was most severe with small seedlings in spring and summer, but was observed throughout the season, and was associated with insect damage to roots and underground stems, and with root and crown rot caused by Pythium and Phytophthora under wet conditions. Missing plants were reseeded in March 2007 and younger plants harvested separately from older plants in October 2007. Subsoiling increased root weight, root diameter, and root length at 277 day (α=0.05) and distance from first branch to crown (α=0.1). Although deep tillage was somewhat beneficial for A. membranaceus, it did not sufficiently loosen soil to yield straight, unbranched roots. The application P with K fertilizer significantly (α=0.1) increased root to shoot ratio for 13-month plants. Astragaloside IV and digoxin (internal standard) were clearly separated and resolved by HPLC-ELSD. Subsoiling significantly increased the concentration of astragaloside IV in all roots except big root of 7-month plants and subsoiling also significantly increased the total content of astragaloside IV in roots of 13-month plants. Small roots had higher concentrations of astragaloside IV than big roots for the same growing period and variety. The higher concentration of astraloside IV was found in 13-month plants than in 7-month plants. Potassium application had a significant (Pr=0.012) interaction effect with P in small roots of 7-month plants on astragaloside IV concentration and K suppressed concentration in absence of P. Phosphorus application significantly (Pr=0.037) affected concentration of astragaloside IV in big root of 7-month plants. The linear interaction effect of P × K was significant (Pr=0.009) in the root of 7-month plants. No P effect was found in small root of 7-month plants, big root of 13-month plants and small root of 13-month plants. Lime had no effect on root growth and astragaloside IV. Varieties AM2, AM3, AM4 and AM5 had good adaptability, root weight (yield) and relatively high concentration of astragaloside IV in the roots and can be chosen to plant in southeastern U. S. as alternative crop.