Date of Award

Fall 12-21-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Eric R Gallandt

Second Committee Member

Brian J McGill

Third Committee Member

Ellen B Mallory

Additional Committee Members

Jianjun J Hao

David E Hiebeler

Abstract

Climate change is expected to impact weed communities in Maine, and the efficacy of tools and tactics farmers use to manage them. Through seedbank sampling and surveys of Maine organic farms, we identified currently rare weeds that are known to be especially abundant or problematic in warmer areas of the USA and might therefore represent an emerging agronomic risk. Many ecological weed management strategies that focus on depleting the weed seedbank are expected to remain effective in a changing climate, and become increasingly important as efficacy of cultivation and some herbicide applications diminish or become more variable. Through field experiments, we evaluated the efficacy of one seedbank management strategy, soil solarization (clear plastic) for stale seedbed creation. We found that two weeks of solarization followed by flaming created an effective stale seedbed, reducing subsequent weed density by 78% as compared to a control prepared with flaming only. In response to farmer questions, we measured solarization’s impacts on soil microbiota, and compared its weed control efficacy to that of tarping (black plastic). Soil biological activity was somewhat reduced by solarization, though results are likely temporary. Solarization was more effective than tarping in one site-year, but tarping outperformed solarization in the other. Overall, solarization is a promising weed management strategy for high-value crops, and one that is likely to remain effective in Maine’s changing climate. Maine is home to a growing population of beginning farmers, who face steep learning curves related to weed management. As a first step toward improving beginning farmer education, we constructed a digital tool called WEEDucator designed to engage users in interactive learning related to ecological weed management. Through a structured educational intervention we found that WEEDucator improved knowledge of weed ecology and management among agriculture students, and was ranked as a preferred learning method. Overall, the findings of this dissertation can aid in the development of outreach materials on climate-resilient ecological weed management practices suitable for farmers in Maine.

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