Revealing the mechanisms behind high potassium efficiency in vegetable soybean through rhizospheric microbial community recruitment and potassium activation

Abstract

The synergistic mechanisms by which potassium high-efficiency (KHE) vegetable soybeans coordinate root exudation and microbial recruitment to enhance potasium absorption under low-K stress remain unclear. Integrating hydroponic and pot experiments, this study analyzed root organic acid exudation, soil potassium availability, microbiome structure, and isolated K-solubilizing bacteria using KHE and K low-efficiency (KLE) varieties. Results showed that under low-K stress, KHE plants exhibited a resilient exudation profile, notably surging malonic acid secretion. This trait mechanistically explains the effective soil K activation in pot experiments, indicated by significant rhizosphere acidification positively correlating with total K depletion. Concurrently, the KHE variety maintained a stable rhizosphere microbiome, characterized by the selective enrichment of specific bacterial (Paenibacillus, Rhodanobacter) and fungal (Penicillium, Aspergillus, Chaetomium) genera. To validate this, we isolated Paenibacillus strains BK1 and BK2 from the KHE rhizosphere. BK2 demonstrated potash feldspar activation (5.7% solubilization efficiency) via medium acidification, significantly enhancing plant growth and K accumulation. Overall, this research reveals a dual mechanism for efficient K utilization: chemical weathering driven by targeted organic acid exudation and the synergistic enrichment of specific rhizosphere microbes.

Graphical abstract

Keywords

potassium / potassium high efficiency / vegetable soybean / rhizosphere / bacterial and fungal community

Highlight

	● KHE variety surged malonic acid secretion and significantly lowered rhizosphere pH.
	● KHE maintained interconnected microbial networks and enriched Paenibacillus taxa.
	● Isolated Paenibacillus strain BK2 solubilized 5.7% of mineral K via acidification.
	● BK2 inoculation significantly increased soybean dry matter and K accumulation.

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