Balancing economy and ecology: A systems comparison of leading organic weed management strategies

Balancing economy and ecology: A systems comparison of leading organic weed management strategies

Summary

This study aims to quantify the benefits and drawbacks of the most prominent organic weed management strategies to ensure that farmers use the most appropriate strategy for their situation. The strategies investigated include 1) cultivation during the critical weed free period of the crop, 2) more extensive cultivation with the goal of zero seed rain, and 3) weed suppression with plastic mulch or 4) organic mulch. Strategies were implemented using yellow onion (Allium cepa, cv Cortland) as a test crop while labor, expenses, weed suppression, soil health, and yield were recorded. First year results indicated that the zero seed rain and organic mulch strategies were more profitable than the other strategies despite their high labor and/or materials costs. Zero seed rain and organic mulch were expected to be poorest performing in their first year but improve over time due to debits to the weed seedbank and benefits to soil quality, respectively. The study will be replicated in the second year and winter squash will be examined in addition to onions. Results will inform the creation of a simulation model and decision tool that will be used in outreach.

Objectives/Performance Targets

Objective 1 was to investigate the hypothesis that four weed control systems (critical weed free period control, zero seed rain, plastic mulch, and organic mulch) have varying short- and long-term effects on yield, soil quality, weed/pest suppression, and profitability. This has been completed for a single field season. The experiment will be replicated next year.

Objective 2 was to determine the factors that motivate farmers to adopt these contrasting weed management strategies. I have initiated this objective through preliminary case-study farm visits and will soon conduct the farmer interviews.

Objective 3 was to develop a decision aid that determines the optimum weed control strategy based on a farmer’s current resources and management goals. This is currently being developed in two ways: 1) through an interactive agent-based model and 2) through a multi-institutional collaboration to develop an Excel-based organic decision support tool.

Objective 4 was to publicize our results through presentations, publications, and extension events so that 100 New England farmers benefit by using our decision aid to inform their management strategy. This will be conducted primarily in Fall 2015, although I will be begin promoting the first year results at the NorthEastern Weed Science Society January 2015 meeting.

Accomplishments/Milestones

This past year, we completed the first season of fieldwork comparing the various weed management systems. Thankfully, no major obstacles were encountered in the implementation of the fieldwork. Many results were as expected (full results in Figure 1). For example, the more extensive weed management strategies controlled weeds better but required more labor and mulch-based strategies benefited the late-season soil quality. There were also several surprising findings. The more labor-intensive strategies were expected to be least profitable in their first year but improve over time due to the investments in soil quality and debits to the weed seedbank. However, the more labor-intensive strategies had a greater profit than the other strategies despite their high labor and materials costs.

In the late summer, case study farms representative of each strategy were visited. The weed competition with crops was documented in photographs and soil samples were taken to complete a germinable weed seedbank assay the following year.

This coming year, the study will be replicated on a new field and winter squash will be planted on the field used in 2014 with the same weed management strategies in place. The second year on the same field may provide hints of the long-term effects of each strategy due to the variation in soil quality and weed seedbank caused by the previous year. I may extend the critical weed free period since that strategy experienced a yield loss despite claims to contrary in the literature. As requested by local farmers, I may also add a components study to examine the effects of using higher quality hay as opposed to the junk hay that is more commonly used for mulch. 

I will also complete the farmer case studies by analyzing their soil quality and weed seedbank as well as conducting interviews to establish their perspective on weed management, their reasons for pursuing each strategy, and unforeseen benefits and drawbacks of each strategy.

I completed a first draft of an interactive agent-based model to demonstrate the results of long-term use of each strategy. I have also been involved with a multi-institutional collaboration to develop an Excel-based organic weed management decision support tool. With fieldwork and case studies completed, I will be able to parameterize and validate my agent-based model and begin using it in outreach presentations.

• Figure 1

Impacts and Contributions/Outcomes

Our first-year results have not yet been replicated, but one of our results that could have a huge impact is that the labor demanding strategies were more profitable in their first year. Specifically, the zero seed rain and organic mulch strategies were expected to gradually become more cost-effective over several years due to reductions in the weed seedbank or benefits to soil quality, respectively. The fact that these strategies were the most profitable in the first year will make adoption much more appealing to farmers. Aside from greater profitability allowing for increased sustainability of operations, these two strategies are expected to have cumulative benefits over time; great reductions to the weed seedbank in the zero seed rain approach should create an ever decreasing need for cultivation and the soil building aspects of the organic mulching strategy should enrich soil and possibly boost yield while reducing fertilizer requirements.

I will be presenting the first-year results at the NorthEastern Weed Science Society January 2015 meeting. To allow for a year of replication, most outreach and dissemination of results will take place after the second growing season of the study. In addition to publications and presentations outlining the findings, an agent-based computer interface will be made available online for farmers to simulate the long-term effects of the different strategies on their farms. The research will also help shape the creation of an Excel-based organic decision support tool in which farmers may input detailed values of their current farm economics to produce a recommendation of which strategy to follow. Overall, it is expected that at least 100 New England farmers will use the decision support tools to inform their weed management strategy.

Collaborators: