Effects of Weeding Frequency on the Yield and Quality of Glycyrrhiza uralensis Fisch in an Arid and Semi-Arid Area of Northwest China

Weeds interfere with agricultural production activities worldwide and have a very serious impact on agriculture and animal husbandry. Identifying a safe and reliable weed control strategy may increase the yield and production net income, and improve crop quality. Licorice is one of the most popular traditional Chinese herbal medicines and has been used for over 2000 years in China. Liquiritin and glycyrrhizic acid are crucial active ingredients. A field experiment was carried out to explore the effects of weeding frequency on the yield and quality of Glycyrrhiza uralensis Fisch in an arid and semi-arid area of northwest China. The experiment consisted of seven treatments: (1) no weeding, marked as WF0, and (2)-(7) artificial weeding using a hoe once every 1, 2, 4, 6, 8 and 10 weeks after emergence, marked as WF1, WF2, WF4, WF6, WF8 and WF10, respectively. We found that a higher weeding frequency resulted in greater plant height, photosynthesis, yield and quality. The highest yield was obtained when the WF1 treatment was applied, while the cost of weeding was high among all treatments. The concentrations of liquiritin and glycyrrhizic acid were increased by 53.24% and 36.57%, with the highest nitrogen metabolism enzymatic activities and quality observed when the WF4 treatment was applied. The WF4 treatment resulted in the largest increase in the net income among all treatments in both growing seasons, with respective increases of up to 71.39% and 78.81%. These findings suggest that weeding once every four weeks could be an effective and sustainable measure to control weeds in an arid and semi-arid area.