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Cover Crops: a solution to protect the Great Lakes

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Media Relations
Agriculture and Agri-Food Canada

Canada’s Great Lakes represent about 20% of the world’s fresh water reserve. We rely on their resources for drinking, farming and general recreation. That’s why it’s important that we keep our Great Lakes clean. To that end, Agriculture and Agri-Food Canada scientist Dr. Xueming Yang is working to keep nutrients used in farming from seeping into the Great Lakes. Not only that, but his research can be applied to improve soil and water health in regions across the country.

Most agriculture uses synthetic fertilizers to provide crops with essential nutrients that help them grow. A problem, however, is that after the crops are harvested, unused nutrients remain in the soil. When it rains, these nutrients can seep into nearby bodies of water and lead to the growth of harmful algal blooms that deplete oxygen and cause aquatic ‘dead zones’. These are called anoxic zones.

While studying the corn-soybean-winter wheat rotation commonly used in fields around Lake Erie, Dr. Yang and his colleagues found that, depending on the soil type, up to 90% of left-over nitrogen is seeping out of the soil into streams, rivers, and eventually entering the Southern Ontario’s Great Lakes, polluting the water and creating anoxic zones.

Luckily, they’ve also found a possible solution; adding cover crops to fields under corn-soybean-winter wheat rotation helps absorb excess nitrogen. Though still in its early stages, hairy vetch and red clover are winter hardy cover crops that have given the most promising results so far, especially when adding one cover crop after the winter wheat harvest and another interseeded into the corn field.

"This is really significant because having two cover crop phases in 3-year corn-soybean-winter wheat rotation resulted in significantly more carbon and nitrogen in cover crop biomass. This practice means that the main crops rely less on synthetic nitrogen fertilizer, and also that the soil profile has less nitrogen before the majority of leaching occurs over the winter. It also increases the organic matter and biodiversity in the soil which helps increase overall soil health."

- Dr. Xueming Yang, Research Scientist, Agriculture and Agri-Food Canada

On top of benefits to water and soil health, this system could be more cost effective for producers too. Hairy vetch and red clover are leguminous plants (also known as Fabaceae). Leguminous plants hold bacteria in their roots that convert nitrogen gas (N2) from the air into ammonium (NH4+) that is usable for the host plant. With the hairy vetch and red clover cover crops absorbing nutrients from the air, Dr. Yang says it will significantly reduce farmers’ expenses for synthetic nitrogen fertilizers, which may also provide them with an organic nitrogen source to enter the organic market.

"If a farmer wanted to change their system from conventional management to organic management, this system could help them. In the last few years, market demand for organic produce has quickly risen so I think producers and consumers could get big benefits from this system."

- Dr. Xueming Yang, Research Scientist, Agriculture and Agri-Food Canada

Change in soil health takes time, and Dr. Yang and his team will have more details in the next few years. However they are hopeful about the potential of the hairy vetch and red clover cover crops to absorb excess nutrients to protect the Great Lakes from anoxic zones as well as implications of the leguminous cover crops fixing nitrogen from the air to feed the crops.

"We’re trying to reduce the impact on the environment and create greener systems, we’re working to make it sustainable and actually feasible for farmers."

- Dr. Xueming Yang, Research Scientist, Agriculture and Agri-Food Canada

Key discoveries/Benefits

Photo gallery

Lush green field of hairy vetch in spring.
Fields of hairy vetch.
Rows of green red clover crops go on until the horizon in spring.
Red clover fields.
Dr. Yang faces the camera in a corn field. He holds a cob of corn in his right hand, still attached to the crop.
Dr. Yang conducting his research in a corn field.

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