HARRINGTON, P.E.I. - A sandblaster loaded with a kitchen staple could give farmers another way to fight stubborn weeds. As potato growers across the country contend with herbicide resistance, scientists at Agriculture and Agri-Food Canada have been exploring alternatives to conventional sprays. A four-year project on Prince Edward Island tested different abrasive products, eventually focusing on baking soda. “It was pretty surprising,” said weed scientist Andrew McKenzie-Gopsill. “We’d go out, spray it in the morning, and then later on in the afternoon we’d just see these black melted weeds all over.” The researchers also tested corn cob grit, finding both materials effective against weeds in potato fields without reducing yields. The two substances were applied separately. Corn grit breaks up leaves and can kill the growing point. With baking soda, McKenzie-Gopsill believes the powder creates tiny abrasions on the foliage and forms an erosive solution that kills the plant. Farmers could use the method as a “second pass” on weeds that survive an initial herbicide treatment, he said. For organic growers, it could complement cultivation, which involves disturbing the soil to control unwanted growth. Even when the technique didn’t completely eliminate the persistent plants, scientists saw a reduction in the number of seeds weeds produced. That could mean fewer the following year. “I think it’s just another tool in a producer’s toolbox,” McKenzie-Gopsill said. “In potatoes and weed management, we have very limited options.” But keeping weeds down this way can drive costs up. The cheapest baking soda McKenzie-Gopsill could find was an industrial, non-food-grade product costing about $1 a kilogram. At an application rate of 480 kilograms per hectare, that works out to nearly $500 per hectare for the powder alone, before other treatments or application costs. “That’s way more expensive than any herbicide is going to be,” he said. It might not be economically viable for growers producing potatoes for chips or french fries, McKenzie-Gopsill added. But it could be worthwhile for crops that fetch higher prices, including organic potatoes and seed potatoes sold for planting. In the first phase of the project, researchers also tested abrasive grits alongside reduced herbicide. It worked, but there was a catch: using lower amounts can encourage herbicide resistance. For the second phase, they instead paired the materials with a bioherbicide, an all-natural product. Again, they found the combination effective, controlling weeds like lamb’s quarters and wild buckwheat well. With the research now complete, the next step is to share the findings with growers and connect with equipment manufacturers about developing a prototype for potato farms.
