Interactions between allelochemicals and the microbial community affect weed suppression

From the report “Interactions between allelochemicals and the microbial community affect weed suppression following cover crop residue incorporation into soil“, from Yi Lou, Adam S. Davis, Anthony C. Yannarell, published in Plant Soil

Because widespread herbicide use in agriculture leads to environmental damage and increased emergence of herbicide-resistant weeds, there is much interest in alternative forms of weed control. The authors of the study work for to understand how soil microorganisms interact with cover crop-derived allelochemicals to suppress weed germination and growth following cover crop residue incorporation.

Authors conducted a time series experiment crossing sterilized and non-sterilized soil with four different residue treatments. They measured weed seed germination rates, radicle elongation, and disease incidence in seed germination bioassays. They also monitored cover crop-derived, isoflavone allelochemicals in these bioassays.

Microbial activity suppressed weed germination and growth for 30 days, while cover crop-derived allelochemicals provided suppression for a limited time. There was an antagonistic interaction between microbes and allelochemicals. This interaction was strongest for water-soluble allelochemicals. Microbial activity can directly suppress weed germination and growth, but microorganisms also indirectly help weeds by degrading cover crop-derived allelochemicals.