Mental models of organic weed management: Comparison of New England US farmer and expert models

Abstract

Weeds are a major challenge for organic farmers, yet we know little about the factors influencing organic farmers' weed management decisions. We hypothesized that farmers and scientist 'experts' differ in fundamental areas of knowledge and perceptions regarding weeds and weed management. Moreover, these differences prevent effective communication, outreach programming and research prioritization. An expert mental model, constructed primarily from interviews with research scientists and extension professionals, revealed expert emphasis on knowledge of ecological weed management as crucial for successfully implementing such strategies. We interviewed 23 organic farmers in northern New England, yielding an aggregate farmer mental model to compare with the expert model. Farmers demonstrated knowledge of the major concepts discussed by experts, but differed in emphasis. Farmers placed less emphasis on ecological complexity than experts. One-third of farmers interviewed discussed the potential role of weeds as indicators of soil nutrient status, a concept of which experts were skeptical. Farmer beliefs about the weed seedbank highlighted potential misconceptions regarding seed persistence, with one-fourth of farmers focusing on the concept that seeds can live for an exceptionally long time in the soil, while experts focused on the concept of the seed half-life. Farmers emphasized the role of experience, both their own and that of other farmers, rather than knowledge derived from scientific research. Farmers considered yield and the cost of time and labor as equally at risk because of weeds, whereas experts predominantly discussed yield loss. During discussions of management, both farmers and experts most emphasized risks associated with cultivation and benefits associated with cover cropping. These results have prompted us, first, to develop new educational materials focused on weed seed longevity and management of the weed seedbank, and, second, to conduct regional focus groups with farmers who prioritize fertility management in their efforts to control weeds, especially manipulations of soil calcium and magnesium.

Organic Farmer Knowledge and Perceptions are Associated with On-Farm Weed Seedbank Densities in Northern New England

“…Farmers were interviewed in fall 2010 to quantify farmer knowledge and perceptions regarding organic weed management. Details of the interview methods were reported previously (Jabbour et al 2013) and are described in brief below.…”

“…We used a semi-structured, openended interview strategy such that all farmers received the same initial prompts, but farmers were asked to clarify or provide more information about the concepts important to them. Interviews were conducted to uncover farmer knowledge, perceptions, and experiences in a way that minimized the influence of the interviewer and provided farmers as much freedom of expression as possible (Jabbour et al 2013;Zwickle 2011).…”

“…Seedbank density was log-transformed to achieve normality. The proportion of hairy galinsoga and crabgrass in the seedbank was calculated based on farmer reports of these species being the most problematic to manage (Jabbour et al 2013). We used two measures to describe weed diversity: species richness (the total number of species per farm) and evenness (relative abundance of species).…”

“…Farmers and experts differed in their perceived risks of weeds, such that experts focused on the likelihood of crop yield loss, but farmers also considered the likelihood of increased time and labor as equally problematic when it comes to weeds. Farmers and experts were largely in agreement regarding risks and benefits of weed management strategies, most often discussing risks of cultivation and benefits of cover cropping (Jabbour et al 2013).…”

“…We hypothesized that mental models would predict seed densities as follows: (1) knowledge in congruence with the scientific expert model, in particular, would be strongly associated with lower seedbank densities; (2) farmers who most often discussed the knowledge categories of systems thinking and ecological complexity, those most emphasized by scientific experts (Jabbour et al 2013), would have lower on-farm seedbank densities; and (3) those farmers who exhibited greater awareness of the risks of weeds, the risks of seedling-focused management practices, and the benefits of seedbank management practices would have lower seedbank densities because of a focus on long-term management strategies. These hypotheses were driven by our overall assumption that farmers who understand ecological systems and the risk-benefit tradeoffs required for seedbank management will have lower seedbank densities.…”