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
- The Great Lakes make up a large part of the world's fresh water reserve.
- Excess nutrients left in soil after harvest can leach into waterways and create
aquatic ‘dead zones'.
- Dr. Xueming Yang and his team at AAFC's Harrow Research and Development Centre have
seen promising results in reducing soil nutrient leaching by using cover crops such
as hairy vetch and red clover.