Botany and Plant Pathology Seminar Series
Speaker: Dr. Eric Gallandt - University of Maine
Topic: Weed Management in Organic Farming Systems: Mental Models, Seedling and Seedbank Management
When: Wednesday, January 15, 2014 at 3:30 pm in WSLR 116

Organic farmers rely on cultivation to reduce weed seedling density and thus loss of crop yield and quality.  Cultivation efficacy, however, is generally more variable and lower than that of a good herbicide program resulting in greater densities of surviving weeds and an increasing weed seedbank.  The simplest response to this problem is to cultivate more, repeating events until the density of surviving seedlings is acceptable, or the crop has a sufficient size advantage.  Another option is to improve cultivation efficacy using innovative tools, careful adjustment, and optimal timing considering soil conditions, crop and weed growth stages.  A final solution is to reduce the initial density of weed seedlings using a systems approach to reducing the weed seedbank.  The central aim here is to reduce or eliminate credits to the seedbank in one or more years thereby exploiting the relatively short seedbank half-lives of many weeds.  Furthermore, disturbance events are deployed with a focus on enhancing seedbank debiting mechanisms, including germination and predation.  We recently completed a qualitative study of organic farmers in northern New England, comparing their beliefs and perceptions of weeds and weed management, i.e., their “Mental Models” to an “expert” perspective.  Weed seedbank management was a notable incongruity between farmers and our expert model.  Whereas experts promote seedbank management as a path towards durable and improving weed management, many farmers consider this a fool’s errand because weed seeds persist for decades in the soil.  Thus, despite considerable research and outreach efforts focused on seedbank management, greater impact will require a thoughtful and skilled educational program that effectively provides farmers with a conceptual understanding of seedbank half-lives and relevant management practices to balance existing knowledge of  maximal persistence of seeds.


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