Interactions between allelochemicals and the microbial community affect weed suppression following cover crop residue incorporation into soil

• Published in: Plant and soil 2016-02, Vol.399 (1-2), p.357-371
• Main Authors: Lou, Yi, Davis, Adam S, Yannarell, Anthony C
• Format: Article
• Language: English
• Subjects: Agricultural land; Agricultural practices; Agricultural soils; Agricultural wastes; Allelochemicals; Allelopathy; Bioassays; Biomedical and Life Sciences; Chemistry; Clover; Control; Cover crops; Crop residues; Crops; disease incidence; Ecology; Environmental aspects; Isoflavones; Life Sciences; Microbial activity; microbial communities; Microorganisms; Phytochemicals; Plant Physiology; Plant Sciences; Plant tissues; Regular Article; Seed germination; Seedlings; Soil microbiology; Soil microorganisms; Soil Science & Conservation; Studies; Suppressive soils; time series analysis; Weeds
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-015-2698-8

BACKGROUND AND AIMS: The objective of this study is to understand how soil microorganisms interact with cover crop-derived allelochemicals to suppress weed germination and growth following cover crop residue incorporation. METHODS: We conducted a time series experiment crossing sterilized and non-sterilized soil with four different residue treatments. We measured weed seed germination rates, radicle elongation, and disease incidence in seed germination bioassays. We also monitored cover crop-derived, isoflavone allelochemicals in these bioassays. We partitioned the total weed suppression into three sources: microbe-only inhibition, residue-only inhibition, and the microbe-residue interaction. RESULTS: 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, while residue fractions containing intact plant tissues retained greater suppressiveness even in the presence of a live microbial community. CONCLUSIONS: Microbial activity can directly suppress weed germination and growth, but microorganisms also indirectly help weeds by degrading cover crop-derived allelochemicals. As a result of these interactions, cover crop-derived weed suppression in agricultural soils shifts from an early allelochemical-dominated phase to a later phase where microbial suppression is more important.