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Understanding and integration of a novel technique to promote depletion of the weed seed bank: How biofumigation acts on different kinds of seed dormancy and weed ecology

Activity summary

The ability of certain plant species to create a persistent seed bank in the soil, avoiding perturbation and harsh environments, is a key phenomenon to understand and to correctly manage for good weed control. The majority of the techniques used to control weeds target plants in life stages other than seed. Being able to reduce weed infestations from the main source, or seed, should be studied with more attention. One emerging method, mostly used to control soil borne pests and pathogens, is biofumigation. This biological process occurs during Brassicaceae decomposition, where toxic molecules (isothiocyanates) are released and negatively affect pests. However, there is a lack of knowledge about the impact of biofumigation on dormant seed, and on the fitness of surviving plants, and so we need to perform more long-term assessments of this practice on the weed community.

In this project, we will focus on the potential of biofumigation to reduce the number of viable seeds in the seed bank, and how this method will shape the weed community. To meet this objective, two experiments will be completed:

• Experiment #1: Assessment of isothiocyanates on seed dormancy and on fitness of the following generation of weeds.
• Experiment #2: Seasonal variation and long-term impacts of biofumigation on weed community and population dynamics.

In the first experiment, the susceptibility of dormant seed to biofumigation will be evaluated, as well as the possible impact on the fitness of surviving weeds after an exposure to isothiocyanate. The second experiment will give us the opportunity to assess the susceptibility of the weed seed bank to biofumigation through the season, assess the effect of repeated biofumigation within the same year on weed populations, and assess the long-term impact of biofumigation on the weed community. The project will be conducted at the Platform for Innovation in Organic Agriculture, Institut de recherche et de développement en agroenvironnement (IRDA), St-Bruno-de-Montarville, Qc. The first experiment will be performed in a controlled environment, were bioassays will be run in continuum for about a year. The second phase will be a four year field study, where different timings of biofumigation and repeated biofumigation will be tested.

Results from this experiment are essential to determine the potential of biofumigation to deplete the weed seed bank. Outcomes of the project will be useful for a large proportion of organic growers, in all plant production systems. At the end of the project, the potential for weed control will be established, and the promotion of this type of green manure will be well supported. This will provide a general framework that could be used to expand results to other production areas (provinces) and organic crop production systems not initially included, and will identify weeding strategies that improve weed control while decreasing hand weeding time.

Materials and Results to Date

• [PDF - 4.9 MB]
  
  • Presented at the 2nd Canadian Organic Science Conference. 2016
    

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