Meng Li, Crop Sciences, University of Illinois-Urbana-Champaign, Urbana, IL and Adam Davis, USDA-ARS Global Change and Photosynthesis Research Unit, Urbana, IL
Effects of arbuscular mycorrhizal fungi (AMF) on plants are context-dependent and vary from positive to negative. In agricultural systems, AMF can differently affect agricultural weeds and crops due to plant host status and soil properties, and have been proposed to potentially contribute to integrated weed management (IWM). We hypothesized that AMF may contribute to IWM through improving the competitive ability of host crops against weeds in the field. To understand this, we carried out a field experiment with contrasting tillage (reduced tillage vs uniform tillage) and cover crop (winter rye vs no cover crop) treatments to create different AMF communities in soils. Reduced tillage can increase AMF richness and abundance in soils due to the reduced intensity of soil disturbance, compared to uniform tillage. The adoption of cover crops will provide diverse and continuous living hosts for AMF to maintain their propagule numbers in soils. In our field experiment, five weed species, including host and non-host species, were planted either alone (no competition) or in competition with corn under combinations of tillage and cover crop treatments. The experiment was a split-plot design and repeated at two locations (IL and MN). For each weed species, absolute competition intensity (ACI) based on shoot biomass and root length colonized by AMF were qualified. Our results showed that 1) Weed ACIs varied according to weed identities, tillage and cover crop treatments. 2) AMF colonization rate explained a relatively low but significant amount of variation in weed ACIs in IL. In conclusion, our results indicate that AMF have the potential to influence crop-weed interference in the field, but the effects of AMF are context-dependent and species-specific. More studies are needed to elucidate the contribution of the specificity of crop-weed-AMF interactions to crop-weed interference within both laboratory and field study systems.