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Mustard crop biofumigation
Vegetable growers are very interested in finding an alternative to chemical fumigation for dealing with soil-borne diseases. Mustard cover crops are being studied as biofumigants. When the tissue of a mustard plant is chopped up in the fall and worked into the soil, there are compounds that release a gas that might help knock down certain soilborne pests and diseases.
Vegetable extension educator Ben Werling at Michigan State University says most of the research has been done with potato crops in the western United States, which have shown some benefit. He did a trial with mustard cover crops on asparagus in Michigan and found no difference. But if you are already growing mustards for other benefits, here’s how to maximize your chances.
"You’re doing it in the fall ahead of planting whatever crop you want to benefit. Or, if you’re thinking longer term, that biofumigant gas, if it is doing anything, is going to be active in September immediately after you incorporate it and then dissipate pretty quickly," says Werling. "So, that’s when it would be providing any pesticidal benefit, ideally knocking down pathogen levels before you plant your crop next year and future years."
Werling says more research needs to be done. Mustard biofumigation results are inconsistent so this is not recommended as a complete alternative to chemical fumigation. But growers can try their own research.
"If you have a really gnarly soil-borne disease issue, definitely don’t rely on this as a solution," he says. "But if they fit well in your rotation, if you can afford to do it, maybe do some strips of it, if you can split a field or do it in some fields and not others for a couple years, then see if you can measure yield so you’ve got numbers and not just your gut feeling."