Fighting Lake Erie’s algal blooms with healthier soils

The rich agricultural history of the Western Lake Erie Basin has taken its toll on the land's soil health. Consequently, the fertilizers used today to keep fields productive and provide essential nutrients to crops are also helping fuel the lake's infamous and harmful algal blooms.

[Link]Jennifer Blesh

But researchers led by Jennifer Blesh of the University of Michigan are working with farmers to reset that first domino and keep it from falling-or at least to minimize its impact-without compromising crop yields. With a new $4 million grant from the Michigan Department of Agriculture and Rural Development, or MDARD, the team is investigating farm management practices to restore soil health.

In addition to reducing the need for fertilizers, these approaches should also help extract carbon dioxide from the air and store it in the soil. In fact, the MDARD grant is part of Michigan's Healthy Climate Initiative and is funded by the Agricultural Nutrient Best Management Voluntary Practices Pilot Program.

"There are a lot of potential win-wins," said Blesh, an associate professor at the U-M School for Environment and Sustainability. "We're working to restore soil to retain nutrients, and that will be even more important as climate change increases the need for farms to be more resilient."

Joining Blesh on the project are Vincent Denef and Brendan O'Neill of U-M; Jeremiah Asher and Christine Sprunger of Michigan State University; Julie Doll of Michigan Agriculture Advancement; and Tom Zimnicki of the Alliance for the Great Lakes.

They're working with a select group of farmers in the basin to better understand the links between soil health and nutrient loss. That knowledge will inform how implementing different conservation practices in fields can best plug those leaks.

"Understanding soil health indicators helps our farmers implement the best management practices for their land and effectively reduce the amount of nutrient loss leaving the farm field and making its way into the Western Lake Erie Basin-all of which fundamentally impacts our state's water quality," said Tim Boring, director of MDARD.

Roots in the ground

The nutrients nitrogen and phosphorus tend to get the most attention when miasmas of microorganisms start clouding Lake Erie's water, and understandably so.

These are the ingredients that feed the bacteria-often referred to as blue-green algae-that can deplete the water's oxygen, muck up the lake and produce toxins that can harm people and their pets.

Blesh and colleagues, however, are also thinking about a different nutrient that isn't talked about as much in the context of algal blooms. They're interested in carbon and, in particular, the carbon found in farmland soils.

Healthy soils have an abundance of carbon and organic material, which is where most carbon is stored in soil. Better soil health leads to better crops, and the soil organic matter also helps retain nitrogen and phosphorus, helping reduce the loss of nutrients from fields to waterways.

Southeast Michigan and northwest Ohio still have good farmland capable of supporting a diverse cast of crops, but the region's soil health is far from what it used to be.

"We're in America's breadbasket and the areas of Michigan that have been used for intensive agriculture have experienced a lot of soil degradation," Blesh said. "We've lost around 50% of the original soil carbon."

As agriculture became more industrialized, it became more efficient and cost-effective for farmers to grow fields with a single type of crop-notably corn or soybeans. These are annual crops that spend only a fraction of a year in the ground.

But the plants are what put carbon in the ground. Their green leafy bits turn carbon dioxide into other carbon-containing compounds through photosynthesis. Plants then shuttle some of these to their roots, where the molecules can exit and help reconstitute soil health.

When fields are empty, then, they lose this critical source of carbon.

"We have long periods of the year when the soil is just bare," Blesh said.

So one of the team's goals is to help farmers keep their fields covered with plants for longer.

As an example, growers could plant winter grains that have living roots in the colder months and are harvested in the summer. Once harvest is complete, farmers could establish a cover crop before winter, which would not be harvested, but would provide other benefits including adding soil carbon, recycling soil nutrients, suppressing pests and attracting pollinators.

There are a variety of approaches to explore, however, which makes the problem more challenging and, to the team working on it, more exciting.

"There's a lot of potential," Blesh said. "Although we are home to intensive corn and soybean production, Michigan is actually one of the most diverse agricultural states in the nation. That makes us an excellent model system for understanding these connections between conservation, soil health, water quality and finding lessons for the Great Lakes and midwestern regions, and for agriculture more broadly."

Simple but complex

Although the idea of introducing more sustainable practices to farmland and seeing which provide the most benefits is straightforward, that doesn't mean it's easy.

For one, the types of changes in soil health the team will be evaluating can take several years to detect. To help accelerate the timeline, the researchers are working with farmers who have documented their history of fertilizer use and land management to establish a baseline.

Understanding how fields lose nutrients is another complex challenge because it depends on a long list of variables beyond soil quality and farming practices. That includes weather, a field's topography and even its history before it was turned to farmland, said Asher, assistant director of the Institute of Water Research at MSU.

Historically, most of the basin was wetlands and, beneath the surface, there are still preferential drainage paths to Lake Erie. Taken all together, this means there's no guarantee any two fields will behave the same.

"The same soil health practice at one location does not always produce the same results at another location," Asher said.

To help account for that, the team is installing edge-of-field monitoring at six farm fields in the basin to directly measure run-off water. It may not sound like many, but it's fairly extensive given how expensive the technology is currently.

"This will be one of Michigan's largest sets of edge-of-field monitoring sites in the state and will be critical to help connect soil health and water quality," Asher said.

In addition to the monitoring, another of the team's goals is to develop robust, inexpensive proxies for direct measurement that can be shared across the basin. The team will track the mass of nitrogen and phosphorus that enters a field through fertilizer or other nutrient amendments. They'll also monitor the mass that departs in harvested crops. The hypothesis is the team can link the difference to indicators of soil health and water quality, which will also be measured, to better model and predict nutrient loss.

This, in turn, will also help the team better understand how changing a farm's management practices ultimately impacts water quality.

The grant support runs for five years. The project will produce valuable insights that can improve agricultural programs and policy design, Blesh said.

Those, in turn, can help foster long-term prosperity in rural communities while promoting environmental sustainability, especially because this project will dovetail with other conservation work happening in the region.

"Our focus is in the field," Blesh said. "But conservation practices like diverse crop rotations and cover cropping are really complementary to other, off-field conservation efforts, such as wetland restoration. In the Western Lake Erie Basin, we'll need a whole landscape-scale approach."

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