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

Yi Lou,Adam S. Davis,Anthony C. Yannarell

doi:10.1007/s11104-015-2698-8

Yi Lou, Adam S. Davis + Show 1 more

Open Access

https://doi.org/10.1007/s11104-015-2698-8

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Abstract

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. 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. 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. 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.

Highlights

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 (Charudattan 2001; Inderjit et al 2005; Liebman and Davis 2009; Weston 1996)
The total allelochemical potential of a cover crop residue is a combination of water-soluble phytotoxins released by residues prior to decomposition, as well as the insoluble phytotoxins released by microorganisms during decomposition (Barnes and Putnam 1986; Harper and Lynch 1982) and the subsequent microbial transformation of these phytotoxins (Barnes and Putnam 1986; Inderjit 2005)
We found microbial infection of seedlings in all non-sterile treatments, Fig. 1 Germination inhibition by red clover residues and soil microorganisms varies over time

Summary

Introduction

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 (Charudattan 2001; Inderjit et al 2005; Liebman and Davis 2009; Weston 1996). Cover crops can suppress weeds through resource and light competition (Liebman and Dyck 1993; Teasdale 1996), disruption of weed life cycles (Moyer et al 2000), physical suppression by cover crop residues (Moore et al 1994), and release of phytotoxic chemicals associated with cover crop residues (Kruidhof et al 2009; Samedani et al 2013; Teasdale et al 2012) These cover crop residueassociated allelochemicals can suppress weed seed germination (Seigler 1996), seedling establishment (Singh et al 2003; Weston 1996), and weed growth rates (Mirsky et al 2011; Wardle 1995). 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

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