To advance the knowledge of soil nutrient management and its influence on the health and productivity of cultivated ginseng, it is essential to elucidate the role of potassium in regulating soil–plant interactions. Potassium (K) is an essential mineral nutrient that plays a crucial role in maintaining plant growth, development and physiological and biochemical metabolic activities. However, the effects of different potassium treatments on the rhizosphere microbial communities and soil nutrients of cultivated ginseng remain unclear. In this study, pot experiments were conducted to explore the comprehensive effects of different K levels (CTRL: 0 mg·kg −1 , K1: 50 mg·kg −1 , K2: 100 mg·kg −1 , K3: 200 mg·kg −1 , K4: 300 mg·kg −1 ) on ginseng rhizosphere soil, microbial community, ginseng quality and saponins. The results indicate that with increasing potassium application rates, the utilization efficiency of ammonium nitrogen (AN), available phosphorus (AP) and available potassium (AK) significantly decreased. Moderate potassium application (50–100 mg·kg −1 ) enhances soil cellulase, amylase, and sucrase activity while significantly increasing ginseng fresh weight and saponin accumulation. High potassium levels (200–300 mg·kg −1 ) inhibit saponin accumulation. Additionally, potassium supplementation (50–100 mg·kg −1 ) altered soil microbial community diversity and structure, with fungal diversity decreasing and bacterial diversity increasing. Community structure became more differentiated, featuring significant enrichment of potential beneficial groups such as Simplicillium , Mortierella , and Gemmatimonas , while groups like Fusarium and Nectria were significantly suppressed. Functional prediction results indicate that potassium application (50–100 mg·kg −1 ) improves the rhizosphere microenvironment by suppressing pathogenic fungal functional groups and promoting bacterial nitrogen cycling processes. Random forest and partial least squares structural equation modeling (PLS-SEM) analyses indicate that potassium application modulates soil enzyme activity and microbial community structure, indirectly promoting ginsenoside accumulation and biomass enhancement. In summary, moderate potassium application (50–100 mg·kg −1 ) can optimize rhizosphere ecosystem functions through a synergistic regulatory mechanism involving microbial communities, soil enzyme activity, and saponin accumulation, thereby enhancing ginseng's nutrient utilization efficiency and medicinal quality. This study reveals the ecological interactions between potassium, soil, microorganisms, and ginseng, while also holding significant implications for optimizing potassium fertilizer application strategies, enhancing the agricultural productivity of cultivated ginseng, and promoting sustainable development. • Revealed the regulatory role of potassium in ginseng continuous cropping soils. • Moderate potassium (50–100 mg·kg⁻¹) improved soil nutrients and enzyme activities. • Potassium regulated microbial communities by enriching beneficial taxa and suppressing pathogens. • PLS-SEM revealed that potassium modulated soil enzyme–microbe networks driving ginsenoside synthesis. • Appropriate potassium (50–100 mg·kg⁻¹) enhanced rhizosphere health and promoted ginsenoside accumulation.
Fang et al. (Fri,) studied this question.