Effects of water and fertilizer combination on the dynamic variations in glycyrrhizic acid levels in distinct regions of Glycyrrhiza uralensis grown in arid territories

Licorice derived from Glycyrrhiza uralensis Fisch. is a significant component of traditional Chinese medicine. Proper irrigation and fertilization are essential for its successful cultivation. To identify the optimal water and fertilizer combination for enhancing glycyrrhizic acid content in various parts of G. uralensis planted in arid regions, we conducted a four-year study from 2019 to 2022. This research took place in the arid and semi-arid areas at the northern foothills of the Tianshan Mountains in Xinjiang, China. We applied an orthogonal two-factor multilevel design to study the effects of water and fertilizer on glycyrrhizic acid content in different plant parts: root, horizontal rhizome, leaf, stem, and rhizome. The study considered variations in irrigation and fertilizer combinations, growth stages, and seasonal changes. Our results showed that the roots contained the highest glycyrrhizic acid concentration. Over time, glycyrrhizic acid levels increased in the leaves, stems, and horizontal rhizomes. Seasonal influences revealed a distinct pattern: the horizontal rhizome showed the highest concentration in spring, while the roots had the highest concentration in summer and fall. The amount of irrigation was found to have a more significant impact on glycyrrhizic acid content than the amount of fertilizer. Furthermore, our mixed-effects analysis indicated that the irrigation amount had a more substantial effect on glycyrrhizic acid content in all plant parts compared to the fertilizer amount. The interaction effects on glycyrrhizic acid content followed the order of stem > rhizome > horizontal rhizome > leaf > root. The glycyrrhizic acid content in each part was significantly higher under the X1Y0-4 gradient than under the X4Y0-4 gradient. This study identifies the optimal water and fertilizer combination for enhancing glycyrrhizic acid content, contributing to the sustainable cultivation of G. uralensis in arid regions.