PubMed · 2026-06-23
Spraying iron, zinc, or copper onto the leaves of medicinal plants doesn't just affect the plant — it ripples down into the soil, reshaping the microscopic communities that govern nutrient cycling and disease risk. Iron sprays boosted beneficial soil bacteria and overall soil health, while copper and zinc sprays did the opposite, encouraging microbes linked to plant disease.
Foliar iron application significantly enhanced rhizosphere soil multifunctionality, including nutrient cycling, while copper and zinc reduced these functions.
Copper and zinc sprays increased the abundance of plant pathogens in the root-zone soil.
The mechanism was microbial: iron promoted efficient, well-connected bacteria (Y-strategists), while copper and zinc enriched larger-genome bacteria negatively associated with soil health (AS-strategists).
