Development of an integrated weed management (IWM) package to mitigate and manage glyphosate-resistance weeds in soybean

Posted on 05.03.2020 | Last Modified 10.04.2024
Lead Researcher (PI): Charles Geddes
Institution: Agriculture & Agri-Food Canada
Total WGRF Funding: $524,831
Co-Funders: Ag Action Manitoba, Manitoba Pulse & Soybean Growers
Start Date: 2019
Project Length: 5 Years

Develop an integrated weed management package to facilitate sustainable soybean production in western Canada and reduce selection pressure for glyphosate resistant weeds.

Project Summary:

General trends among this suite of experiments suggest that agronomic practices used to promote greater soybean yield under weed-free conditions tend to also result in higher yields when under weed interference. Environmental conditions played a strong driving role in the efficacy of the various integrated weed management (IWM) tools, where the tools that were effective for mitigating crop yield losses due to weed interference tended to vary among site-years. This suggests the critical importance of implementing multiple cultural weed management tools together in an IWM program, thereby increasing the chances that at least one or more tools are contributing positively to weed management and yield loss mitigation each year. This research identified several cultural tools for IWM in soybean production. When used in combination, these tools could contribute to lower selection pressure for glyphosate-resistant weeds by reducing the survival, growth, and seed production of weeds that survive post-emergence herbicide applications in soybean. In many cases, these cultural tools improved soybean productivity under both weedy and weed-free conditions, meaning that they will contribute positively to the cropping system regardless of whether they are used for proactive mitigation of herbicide-resistant weeds or reactive management after they are already present in fields. Taken together, this research project provides agronomic recommendations for prairie soybean farmers to help them increase soybean productivity and mitigate herbicide-resistant weeds that threaten the agricultural value chain. Future research should address the economics of implementing these practices in the short- and long-term. While short-term economics are important for many farmers, economic analyses assessing the implementation of IWM programs should also assess long-term profitability by placing a value on reducing selection pressure for herbicide resistance. For example, while increasing soybean target densities above the currently recommended levels did help to improve weed management in the current research, the high expense of soybean seed may make the implementation of this IWM tool infeasible in the short-term. However, decisions regarding the implementation of IWM practices should consider the cost of herbicide-resistant weeds in the future combined with the contribution of the IWM practice to herbicide-resistant weed mitigation to fully assess the value of proactive IWM.