The Effects of Fertilizer and Deep Tillage on Growth, Root Development, and Astragaloside IV in Astragalus membranaceus.

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, two field experiments were planted in beds to test the effects of (1) deep tillage (subsoiling vs no subsoiling) and (2) 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. Each experiment consisted of a randomized complete block design with four replications. The fertility study was a 3X3 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, 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 and crown diameter, increased root length at 277 day (p=0.05) and distance from first branch to crown (p=0.1). The concentration of astragaloside IV in 7-month and 13-month plants was 0.18 mg g^-1 and 0.67 mg g^-1 respectively with subsoiling, compared to 0.13 mg g^-1 and 0.45 mg g^-1 respectively with no subsoiling. Phosphors fertilizer application significantly (p=0.1) increased root weight among 7-month plants. Without K fertilizer application, P increased root length and root diameter among 7-month plants. The application P with K fertilizer significantly (p=0.1) increased root to shoot ratio for 13-month plants. The lime effect was not significant. The concentration of astragaloside IV in 13-month plants was highest at 29 kg P ha^-1+ 56 kg K ha^-1.