Effect of microbial fertilizers on root nutrient content and yield quality of Glycyrrhiza uralensis

To solve the problems of soil nutrient imbalance, low nutrient absorption efficiency, and low and unstable yield and quality during Glycyrrhiza uralensis cultivation, in this study, Bacillus amyloliquefaciens (J), Bacillus subtilis (K), and composite bacterial fertilizer (W) were applied to G. uralensis under rotating and continuous cropping. The effects of microbial fertilizers on the yield and quality of G. uralensis and the root and soil nutrient content were studied, to provide a theoretical reference for efficient fertilization of G. uralensis and to improve its yield quality. The results showed that compared with CK treatment, the J, K, and W treatments increased the yield of rotating G. uralensis by 22.53%, 36.92%, and 22.92%, and increased the yield of continuously cropped G. uralensis by 16.17%, 41.94%, and 23.73%, respectively. The content of glycyrrhizin in rotating G. uralensis increased by 0.98, 0.79, and 0.24 percentage points, and the content of liquiritin increased by 0.42, 0.28, and 0.27 percentage points, respectively. The content of glycyrrhizin in continuously cropped G. uralensis increased by 0.54, 0.32 and 0.77 percentage points, and the content of liquiritin increased by 0.12, 0.26, and 0.30 percentage points, respectively (P < 0.05). The J, K, and W treatments all increased the nutrient content of nitrogen, phosphorus, and potassium in G. uralensis roots by increasing the soil nutrient content of G. uralensis, thus increasing the yield and quality. The K treatment significantly increased the content of ammonium nitrogen, quick phosphorus, and quick potassium in soil with rotation and continuous cropping of G. uralensis by 24.82%～30.53% and 24.61%～35.59%. Thus, the total phosphorus content of rotated and continuously cropped G. uralensis roots increased by 83.83% and 48.70%, respectively, and the total potassium content increased by 63.37% and 58.70%, respectively, achieving the effect of increased yield and quality. The comprehensive application of Bacillus subtilis gave the best results and is a promising strategy for G. uralensis cultivation.