Abstract
Owing to overexploitation, wild resources of Astragalus mongolica, a Chinese herbal plant that is widely distributed in the arid and semi-arid areas of Northern China, have gradually become exhausted, and therefore, commercial cultivation is increasingly important to meet the growing demand for astragalus and reduce the pressure on wild populations. Nitrogen level is an important factor that affects the yield and quality of A. mongolica. However, uniform standards for fertilization among production areas have not yet been determined. In this study, the effect of nitrogen fertilizer treatment on the yield and quality of A. mongolica in the Qinghai-Tibet Plateau was explored using a control treatment (no added nitrogen, N0) and five different nutrient levels: 37.5 kg/ha (N1), 75 kg/ha (N2), 112.5 kg/ha (N3), 150 kg/ha (N4), and 187.5 kg/ha (N5). According to grey relational analysis, the optimal nitrogen fertilizer treatment was the N4 level followed by the N5 and N2 levels. Nitrogen fertilizer significantly increased the root biomass, plant height, root length, and root diameter. However, nitrogen fertilization had no significant effect on the content of Astragaloside IV and mullein isoflavone glucoside. The content of ononin and calycosin continually accumulated throughout the growing period. The results showed that the ononin and calycosin content under N4 and N2 is higher than other levels and there is not significantly different between different nitrogen fertilizer levels about them. The content of formononetin decreased gradually with the progression of the growing season. The optimal nitrogen fertilizer treatment for A. mongolica is recommended to be 150 kg/ha and the content of active compounds and yield were observed to reach the maximum in October.
Highlights
Astragalus mongolica (A. mongolica) is a multipurpose leguminous herb that has been widely used inChina for thousands of years as a medicinal and food plant because of its remarkable pharmacological efficacy [1]
The highest plant height was observed in the N4 treatment group, which peaked in August, and significant differences were observed between the five levels of nitrogen fertilizer
The maximum plant heights peaked in August for the other groups, except for the N2 and N4 treatment groups, in which the maximum plant heights peaked in September and October, respectively
Summary
Astragalus mongolica (A. mongolica) is a multipurpose leguminous herb that has been widely used in. China for thousands of years as a medicinal and food plant because of its remarkable pharmacological efficacy [1]. The farmer breeds seedlings in the first year, and plants and harvests it in the second year. This species is used in the textile and pharmaceutical industries as an industrial raw material. Owing to the toughness and preservation of astragalus fiber, the practicability and effectiveness of textiles made from it are greatly improved [2]. The medicinal value of Molecules 2020, 25, 381; doi:10.3390/molecules25020381 www.mdpi.com/journal/molecules
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