Short-term magnesium application boosts tea quality through aroma compound enrichment, stress resistance improvement, and rhizosphere microbiome modulation

The application of magnesium (Mg) fertilizer affects soil microbial community diversity, but research on the relationship between soil microorganisms and key components of tea aroma remains insufficient. This work characterizes Mg amendment effects on plant physiology, volatile biosynthesis, and harvest quality parameters. Four Mg concentrations (0, 100, 200, 300 mg kg−1) were tested in a 90-day pot study. We analyzed tea plant growth, nutrient uptake, stress resistance, tea quality (including volatile compounds), and soil properties (physicochemical characteristics and bacterial communities). This study demonstrates that moderate Mg application (200 mg kg−1) optimally enhances tea quality through a coordinated soil-microbe-plant mechanism. Mg amendment improved soil physicochemical properties by increasing pH and cation exchange capacity while reducing aluminum toxicity. These changes drove a shift in microbial community structure, enriching beneficial taxa such as Sphingomonadaceae and enhancing microbial network complexity. The restructuring of the soil microbiome facilitated nutrient uptake and strengthened the plant's antioxidant system, ultimately elevating the synthesis of key aroma compounds. The MM treatment significantly increased the levels of characteristic volatiles-including phenylethyl alcohol, and methyl salicylate-imparting a distinct sweet and fruity aroma profile to the tea. Our findings establish a mechanistic link between Mg fertilization, soil microbial communities, and tea quality, providing a science-based strategy for aroma-oriented cultivation management.