Nutrient distribution in various tissues of Licorice (Glycyrrhiza glabra L.) and the influence of soil fertility on the levels of its bioactive compounds

Abstract

This study aimed to optimize the production of licorice (Glycyrrhiza glabra L.) in field conditions using two licorice ecotypes and various types of nutrient sources. Licorice yield, leaf and root nutrient content, and its bioactive compounds were assessed. Mycorrhiza inoculation resulted in the highest rhizome dry weight in the Lalehzar (101.3 g) and Kermanshah (395.6 g) ecotypes in the first and second years, respectively. Rhizome dry weight was higher than the roots in both ecotypes. Two years old Kermanshah ecotype exhibited the highest root dry weight by using urea. The harvest index increased in Lalehzar ecotype by application of vermicompost in the first year and cow manure coupled with plant growth-promoting bacteria (PGPB) in the second year. Nitrogen content in leaves and roots significantly increased in the Kermanshah ecotype using cow manure and PGPB. Application of mycorrhiza (in Lalehzar ecotype) and cow manure combined with urea (in Kermanshah ecotype) led to leaf phosphorus (P) content improvement. The highest root P content in Lalehzar and Kermanshah ecotypes achieved by using cow manure and urea, respectively. Fertilization by urea and mycorrhiza led to higher leaf potassium (K) content in Kermanshah and Lalehzar, respectively, while urea yielded the highest root K content in the Kermanshah ecotype. Root glycyrrhizic acid (GA) content peaked in the Kermanshah ecotype with cow manure and PGPB (138 and 372.8 mg g-1 DW in the first and second years, respectively). Rhizome GA content performed better in the Lalehzar ecotype using cow manure and PGPB (191.34 mg g-1 DW, first year) and in the Kermanshah ecotype with cow manure and urea (239.62 mg g-1 DW, second year). Fertilizers had not significant effect on glabridin (GL) content. Notably, GA and GL exhibited a negative correlation with potassium and nitrogen. This study highlights the importance of balanced nutrient management for licorice cultivation.