Effect of Irrigation Pattern and Irrigation Level on Growth of Glycyrrhiza inflata and the Medicinal Quality of its Root

Abstract

Background: Although both the root and rhizome of Glycyrrhiza inflata have been used as medicinal material, the sales volume and price of its root are much higher than its rhizomes. Limiting the growth of liquorice rhizomes while improving the yield and quality of its root has become an important problem. Methods: Two irrigation patterns (surface drip irrigation and subsurface drip irrigation, i.e. DI and SDI) and three irrigation levels (40%-50%, 60%-70% and 80%-90% of the maximum soil water capacity) were used in this study. Result: The plant height, crown width, root length, root biomass and concentrations of the five medicinal components (glycyrrhizic acid, glycyrrhetinic acid, glycyrrhizin, liquiritigenin and isoliquiritigenin) of the SDI treatments were significantly higher than those of the DI treatments. The above parameters reached their maximum under the SDI90 treatment (SDI with 80%-90% of the maximum soil water capacity). The rhizome growth of the liquorice was promoted with an increase in irrigation amount, but the biomass of the rhizomes under SDI treatment was significantly lower than that under DI treatment. Thus, the regime of SDI with a relatively high water supply can effectively promote the yield and medicinal quality of liquorice roots, while inhibiting the development of its rhizomes.