Preventions & programs

Sunday, October 9, 2022

An update on nutrient runoff

by Kristen Lutz

Lake Erie, Lake St. Clair and surrounding watersheds continue to be affected by nutrient runoff from farms, leading to well-documented increases in algae blooms.

Agricultural nutrient runoff contains nitrogen (N) and phosphorus (P), which continues to be a significant source of water pollution leading to these blooms.

Better Farming interviewed experts on what programs are in place to address the ongoing issue, and what producers might do on their farm.

"What happens is we have a lot of phosphorus in the environment, and why does it build up? It could be from over-application of fertilizer, build-up from excess manure on fields – but it can also happen if there are cows in the stream," says Merrin Macrae, professor in the department of geography and environmental management at the University of Waterloo.

"As the algae decompose, they release bacteria through the dead organic matter and this process depletes available oxygen in the water. This low oxygen has negative implications for fish and other aquatic life. Some forms of algae release toxins which limit the use of water for human consumption and recreation," explains Tatianna Lozier, agriculture soil and water quality technician with Upper Thames River Conservation Authority.

"Any time water is leaving a field, nutrients are leaving with it."

Nutrient runoff is causing problems across North America.

The Gulf of Mexico is an extreme example.

Runoff drains into the Mississippi River, which empties into the Gulf. These nutrients are considered a major contributor to the Gulf's vast "dead zone," an area with little to no oxygen, which can kill marine life.

Researchers at Louisiana State University have measured the Gulf's dead zone to be 6,334 square miles.

Illinois and Iowa are the largest contributors to ag runoff into the Gulf.

The research has resulted in a nutrient loss-reduction strategy that aims to reduce N and P losses by 45 per cent by 2035.

Ontario's algae concerns

Phosphorus is the primary component in creating algae blooms.

"In free water systems, once you increase P, the growth and production of the algae just explodes. N is important because it can affect the type of algae and bacteria that are growing, and if they are toxic or not," says Macrae.

"It's important to remember that these nutrients can come from a lot of different places in the environment, including point sources," she adds.

"Point source pollution comes from one specific identifiable source such as pollutants discharged from a pipe, ship or factory, or sewage treatment facility," says Mike Buttenham, sustainability and environmental lead with Grain Farmers of Ontario.

Non-point sources are a result of "rainfall or snowmelt moving across a landscape, where it picks up natural and human-made pollutants, depositing them into lakes, rivers or wetlands," he adds.

"Agriculture is obviously a significant source of non-point runoff," explains Macrae.

Snowmelt or after a rainfall is when most nutrients leave a field. They can leave in their dissolved form, invisible to the human eye, or they can leave through erosion along with sediment.

"You can imagine a stream that looks like chocolate milk when it leaves a field – there is a lot of P in that water," explains Macrae.

Tile drainage systems are also contributing to nutrient runoff.

"We didn't used to worry about groundwater because the soil will hold onto that P, but unfortunately, some of that water can get easily into tile drainage and bypass the soil and end up in the waterways," says Macrae.

"There's also something called a legacy effect – what was done on the land years ago can still affect the nutrient runoff today, and nutrients that are in either stream or lake sediments can be re-released over time," says Lozier.

It's a complex situation.

"The Lake Erie watershed is the most unique watershed in the Great Lakes Basin," says Buttenham.

He refers to the 78,000 kilometres that drain into Lake Erie and explains that 63 per cent of the watershed is used for agriculture.

Projects in place

The Government of Ontario and Conservation Authorities have several projects currently in place to protect waterways.

The Canada-Ontario Lake Erie Action Plan (LEAP) aims to reduce P entering the central and western basins of Lake Erie by 40 per cent, explains OMAFRA spokesperson Belinda Sutton.

The plan includes more than 120 actions to reduce P and algae blooms. These actions are divided into five categories: reducing P loadings, ensuring effective policies, programs and legislation, improving the knowledge base, educating and building awareness, and strengthening leadership and coordination.

One of the major focuses of this program is encouraging effective techniques to keep phosphorus on farmland.

OMAFRA has contributed "$5.5 million in funding to support the implementation of more than 550 on-farm best management soil health improvements," states Sutton.

The Ontario Soil and Crop Improvement Association also has a program that works directly with farmers. The Lake Erie Agriculture Demonstrating Sustainability (LEADS) initiative allows farmers to work one-on-one with a participating certified crop advisor or professional agrologist, free of charge, to establish best management practices to reduce the risk of nutrient runoff – all while improving soil health and making a difference in their bottom line.

On a larger scale, the Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health was renewed last year. This federal-provincial agreement outlines how the government will protect, restore and conserve the Great Lakes Basin ecosystems. It ensures that both the provincial and federal governments will work together to meet the obligations under the Canada-U.S. Great Lakes Water Quality Agreement.

Farmers that aren't located in the Lake Erie and Lake St. Clair areas can contact their local conservation authorities for more details on water quality improvement programs in their region.

On-farm management

Producers' best management practices can vary.

"We want to make sure we are using the right practices in the right places," says Macrae. "The top three things that you can do may not be the same things that another farmer can."

Buttenham agrees. "It's a very complex topic and there isn't a one-size-fits-all approach. Each farm and its farmers are unique with the crops they grow, soil type, climate and weather, and access to equipment."

Mitigation techniques, like the 4R Nutrient Stewardship program, ensure producers aren't over-applying crop inputs. Applying the right source, at the right rate, at the right time and in the right place, ensures optimal nutrient use with reduced environmental loss.

"Certain practices like spreading nutrients, including fertilizer and manure, can have negative consequences to water quality when done on frozen or snow-covered ground," explains Buttenham.

"Initiatives like the 4R Nutrient Stewardship program work to avoid these poorly timed nutrient applications to ensure optimal plant uptake while reducing the risk of runoff."

Lozier explains that this is also true for timing of manure application.

Farmers should ensure they aren't applying manure while the ground is still frozen or before a major rainfall event. Both situations can lead to substantial nutrient losses.

"Optimizing fertilizer application is going to be an environmental, agronomic and economic benefit for a farmer," adds Lozier.

Once fertilizer is applied, it's important to prevent nutrient loss through sediment. Tactics that prevent erosion, like no-till, can ensure this.

"In undulating terrain, I think no-till is especially effective," says Macrae. "I think it's a great idea everywhere because it's going to help you keep the soil on the field – it's particularly good in areas to prevent erosion."

Lozier agrees. "If you look at a corn field after harvest that's no-till, there's going to be a lot of residue left on the surface, which is going to help slow water and soil erosion."

Similarly, cover crops can reduce runoff, Macrae says, by protecting the ground's surface.

"When rain and snowmelt happen, cover crops protect the soil from the energy of the raindrop or from flowing water.

"The cover crops will build a root system and facilitate the water to enter the soil. But also, there is friction, and the cover crops will slow the flow of the water so that the water can't pick up speed and pick up the soil with it.

"They are very important for preventing erosion and particulate P losses."

Cover crops can also take up nutrients. "When plants are growing, they're going to take up N. So, if you think about cover crops and think about the timing when fields are bare right after harvest, planting something that's hardy and that can stay in the ground over the winter is a good solution," advises Lozier.

"A common one used around (Upper Thames) would be cereal rye, but there is also oat and radish that scavenge for nutrients."

On-farm water quality management is producer specific. Your local conservation authority and certified crop advisor can offer solutions to prevent nutrient runoff that best fit your operation.

"The first line of defense should be on-field. Apply just enough P to grow your crops, don't over-apply – this will work everywhere.

"Everything else – tillage, cover crops, when you apply, how you apply – is going to differ depending on where you live, and you need to target what works for you," says Macrae. BF