Role of vermicompost and biochar in soil quality improvement by promoting Bupleurum falcatum L. nutrient absorption

Abstract

Bupleurum falcatum L. has gained attention due to its medicinal value in its root. B. falcatum was continuously cultivated and intensively chemically fertilized in order to attain a high yield, which reduced the soil quality and caused continuous cropping problems. Thus, there is a significant impact on S. baicalensis yield and quality. To solve this problem, soil with 0 or 3 continuous cropping years (0- and 3-year soil) was fertilized with several organic materials, which are Bacillus subtilis, Bacillus mucilaginosus, humic acid fertilizer, biochar, and vermicompost. The experiment examined the effectiveness of B. falcatum's growth and nutrient uptake under various organic materials. It was shown that organic materials improved soil fertility and promoted the growth and nutrient uptake of B. falcatum. The combination of vermicompost and biochar had a better improvement effect. It increased soil nutrients by 23.8%–73.3% (0-year soil) and 24.6%–71.1% (3-year soil), respectively. In two types of soil, both microbial number and enzyme activity substantially increased. The B. falcatum shoot and root biomass with vermicompost was increased 74.8%–84.5% (without biochar) and 41.8%–71.1% (with biochar) in two types of soil. Vermicompost and biochar also significantly promoted the root development of B. falcatum. The root length increased by 13.3%–66.7%, the root diameter by 38.6%–84.8%, the root volume by 8.4%–61.3%, and the specific root length varied by −171.9% to 3.1% when compared with the control. The nutrient (N, P, and K) concentrations in shoots and roots changed from −3.9% to 67.2% and from 1.4% to 53.5%. All the findings demonstrated that long-term continuous cropping caused cropping obstacles, deteriorated soil quality, and inhibited the B. falcatum growth. Applying organic fertilizers, such as vermicompost and biochar, can help to improve soil quality, increase soil nutrients, promote the growth and nutrient absorption of B. falcatum, and eliminate continuous cropping obstacles.