Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Science




Thorn, Richard G.


Herbicide use within conventional agriculture has contributed to greatly increased crop yields since its widespread adoption, but environmental concerns regarding overuse and reliance on selective herbicides continue to mount. Using five fungal species and two crop residues in a factorial design, I created a novel slurry to control weeds through inhibition by the mycelial mat formed after application to soil. I monitored weed stem counts and the strength of the mycelial mat under the treatments. Additionally, as a proxy for crop yield, I measured the wet and dry mass of crop plant grown under application treatments. Weed prevalence was significantly reduced when compared to a bare soil control, but not when compared to a substrate only control without fungal inoculum. Similar strength values were recorded between treatments and control, suggesting poor colonization of the substrate under greenhouse and field conditions. No significant weed reduction was achieved in field trials.

Summary for Lay Audience

Greater agricultural yields are required to continue to meet the global food demands of the increasing human population. One tool employed by modern agriculture to help meet demand is the use of herbicides to control weeds which, left uncontrolled, compete with crop plants for energy and resources. Herbicide use has contributed to greater realized yields, but concerns exist regarding negative environmental impacts and over-reliance causing decreased effectiveness of these herbicide regimens. In this study, I tested a novel approach to control weeds without traditional herbicides. I formulated liquid slurries with different combinations of fungal cultures and waste from Ontario agricultural crops to be applied on crop fields. To determine effectiveness, I measured the number of weeds present in treated plots, plots covered with crop waste only, and uncovered plots. I also measured the strength (penetration resistance) generated by the slurry once applied, as well as crop plant weights to detect any negative or positive effects on plant growth. I found the treatments greatly reduced weed counts compared to uncovered plots but provided similar weed reduction compared to plots covered with just crop waste. The slurry did not generate a fungal mat of significant strength compared to bare soil, nor were there any significant changes to weights of the crops grown. Although this trial did not achieve weed control using fungal growth, alternative combinations of fungi and crop wastes may yield greater power to control weed growth, and different applications may yield other economic and environmental benefits, such as reduction of crop residues and winter soil erosion, and improvement of soil organic matter.

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