Rhizosphere Engineering by Root Exudates: High-Yielding Alfalfa Recruits Functional PGPR to Sustain Soil Nutrient Availability Under Long-Term Cultivation.

Root exudates from high-yielding alfalfa in an 8-year continuous system enriched functional PGPR and increased soil organic carbon by 8.64%, total nitrogen by 6.01%, and labile phosphorus by 1.62%.

• Why it matters: Soil nutrient transformation capacity limits sustainable productivity in perennial cropping, but how high-yielding crops regulate rhizosphere microbial assembly to maintain nutrient availability is unclear.
• What they did: In rhizobox experiments, alfalfa root exudates enhanced growth only with an active microbiome, while high-yielding cultivars enriched Ensifer, Pseudomonas, and Bacillus; isolated strains showed N fixation, P solubilisation, and IAA production.
• The result: Metabolomics linked exudates enriched in maltopentaose, maltotetraose, taurine, N-acetyl-L-leucine, and asparagine to chemoattractant-driven PGPR proliferation and biofilm formation, supporting N fixation and P transformation for sustained productivity.

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