Soil rhizobia promote plant yield by increasing tolerance to pests and pathogens under field conditions

Summary

This field experiment demonstrates that soil rhizobia promote legume yield through multiple pathways beyond nitrogen fixation, including enhanced tolerance to the pea aphid and an aphid-borne virus. Using a manipulated soil treatments design, the authors show that rhizobia inoculation reduced pest pressure and pathogen incidence more effectively than synthetic nitrogen fertilisation alone, with structural equation modelling indicating that pest and pathogen suppression was a substantial mechanism driving yield benefits. The findings suggest soil microbial communities exert strong indirect effects on aboveground crop protection and productivity.

UK applicability

The findings are relevant to UK pea and legume production, particularly given the increasing agronomic and environmental interest in reducing synthetic inputs. However, the study was conducted under field conditions in a single location (likely North America based on author affiliations); UK growers would need to assess whether results translate to different soil types, climates, and pest/pathogen pressures characteristic of British farming conditions.

Key measures

Pea aphid (Acyrthosiphon pisum) abundance; pea enation mosaic virus incidence; pea yield; structural equation model path coefficients comparing effects of rhizobia versus synthetic nitrogen fertilisation

Outcomes reported

The study measured aphid abundance, pea enation mosaic virus (PEMV) incidence, and pea yields across four soil treatments: untreated, sterilised, sterilised with nitrogen fertiliser, and sterilised with rhizobia inoculation. Structural equation modelling was used to quantify direct and indirect effects of rhizobia on plant tolerance and yield.

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