Recently two reports arrived in my email. The first was notification of an update to the Minnesota Pollution Control Agency’s Nutrient Reduction Strategy (NRS). I didn’t know we had one. I read it carefully.

The second was a piece called “Replumbing Minnesota: How Agricultural Drainage Alters Rivers and Degrades Water Quality.” It’s a report from the nonprofit Minnesota Center for Environmental Advocacy (MCEA), a group of attorneys who watchdog state government on environmental issues.

Together, the two reports opened my eyes about the deeply entrenched pollution problems in farm country and the challenges we face in addressing them.

The main culprits are nitrogen and phosphorus. These are basic nutrients needed for plant growth, but when levels get too high, they can cause problems for streams and rivers: they can rob oxygen, promote algae growth, kill aquatic life, and pollute drinking water.

Also, since so many farmers shifted to corn and soybean rotations in the 1980s, (corn and soybean acres have increased by about 140,000 acres per year since 1982) they have installed miles and miles of drainage pipes to improve their fields for corn. This has produced a lot of corn but also faster water flows and “flashiness”—even heavier flows after storms.

The 1980s is also when farmers started growing corn for ethanol. Currently, about 30 to 40 percent of Minnesota corn goes to ethanol plants.

As we would expect, state agencies are trying to help farmers deal with both problems. So far, those efforts are yielding modest improvements.

The problem

The Minnesota Department of Agriculture says agriculture contributes about three-quarters of the total nitrogen in the state’s rivers, and about half of the phosphorus load. Phosphorus pollution has been dramatically reduced, notably after a 2005 state law restricted phosphorus in lawn fertilizer and through better wastewater treatment. The NRS suggests that “because so much work has already been done to reduce phosphorus throughout the decades, it will be challenging to further the progress and complete the needed reductions.”

It’s the opposite for nitrogen.

Farmers are applying more and more nitrogen to their corn fields. In 2022, about 620,000 tons of nitrogen were applied to farmland. Corn crops flourish under this regimen, but the impacts for the environment are grave.

We tend to forget about the hypoxic zone in the Gulf of Mexico until we’re reminded by a yearly report on how big it is. That dead zone is caused primarily by nutrients flowing down the Mississippi River from upstream farm states, starting with Minnesota, which contributes the sixth highest nitrogen load to the Gulf. A similar dead zone plagues Lake Winnipeg in Manitoba, fed by the Red River along the border between Minnesota and the Dakotas. Local impacts include harm to aquatic life, blue-green algae growth, and high nitrogen levels in drinking water in southeastern Minnesota.

The NRS outlines various best management practices (BMPs) designed to reduce these impacts. There are 22 approved practices for removing nitrogen and 20 for phosphorus. They include:

• Conservation crop rotation (adding small grains or perennials into rotations)
• Reduced tillage methods such as strip-till
• In-field nutrient management (fertilizer and manure precision/efficiency)
• Drainage water recycling (storing and irrigating drainage waters)
• Wetland installation
• Perennial crops and pastures as working lands
• Cover crops

The report says pretty much any piece of land can use one or more of these methods. “Since 2014, over 4 million acres of Minnesota land have been treated by new practices adopted through government programs alone (roughly 18% of cropland),” according to the report. “These additional practices follow decades of conservation work and improved fertilizer efficiencies,” it adds.

If these practices are continued, the report estimates they would result in 5 percent reduction in nitrogen and 8 percent reduction in phosphorus in the Mississippi River as it flows out of Minnesota. Obviously, more is needed.

Drainage for corn

Meanwhile, farm drainage is dramatically changing the landscape and water systems in some rural areas. Minnesota farmers install drain tile (actually, long flexible plastic piping) to dry the soil out quickly in the spring so they can plant corn. They add over 100 million feet of subsurface drainage pipe each year. “In many counties, there are more miles of underground pipe than roads,” says Carly Griffith, water program director at MCEA.

The problem is most severe in southwestern and southern Minnesota. More than 62 percent of the watersheds of the Blue Earth, LeSueur, and Watonwan Rivers have been altered for drainage.

Corn crops respond well to this treatment, but it also dramatically speeds the flow of water, along with the pollutants it carries. As the water gushes into small streams and rivers, it erodes banks and channels and carries more sediment downstream, all the way to the Gulf of Mexico. Ironically, this phenomenon offsets some of the gains made by farmers using best management practices.

A recent U.S. Census of Agriculture showed Minnesota with eight of the top ten counties in the country with drainage increases. “So, we’re really the epicenter of impacts in the upper Midwest,” Griffith says. Research also shows these heavily drained areas are less resilient than undisturbed areas to the increasing intense storm events climate change is bringing us.

Both of these reports call for increased use of the best management practices. Most drainage is under the control of county government or drainage authorities. Farmers who want to add or expand their drainage apply to the local drainage authority. “There’s a good opportunity at that point to incorporate more of the management practices, says Griffith. The report recommends the state create a general permit system similar to permitting for municipal stormwater management.

“We’ve done enough research to move forward and implement proven practices,” says Griffith. “We need continued investment in voluntary programs that have shown success, and we need to apply regulations in the most-affected areas.”

Experts are cheered by the near-total compliance with the buffer requirements approved during the Dayton administration. But it’s not a silver bullet, says Griffith. “Buffers will not solve the problems caused by drainage. The water passes under the buffers via subsurface drain tile.” On the other hand, farmers can change where the drain pipes deliver their load. Water delivered into the buffer instead of into a creek or ditch will be slowed down and natural processes in the berm will clear some of the nitrogen. This is called saturated buffering.  

Another effective method that could be adopted more widely is two-stage ditches. These mimic the benefits of a natural stream channel, allowing the excavated ditch to heal itself over time. It’s basically like creating a stream within a stream. The upper ditch is planted with vegetation that cleans the water that overflows into it.

Certified farms

The Minnesota Agricultural Water Quality Certification Program is a voluntary program designed to incentivize farmers to adopt some of these practices. Begun in 2014, the program has enrolled more than 1500 farmers on about a million acres. Experts examine the entire farm and its operations and make suggestions for mitigating risks to water quality. Landowners who treat all risks to water quality are certified and are deemed to be in compliance with any new water quality laws or rules for 10 years. Farmers often receive reimbursement for the cost of the work from federal or state farm programs. Farms are exempt from Clean Water Act rules. But two state rules have been implemented since the beginning of the certification program, the 2015 buffer law championed by Governor Dayton and the 2019 Groundwater Protection Rule restricting nitrogen application seasonally. Brad Jordahl Redlin directs the certification program; he says, “We already exceeded what Governor Dayton’s buffer law asked farmers to do, and our certified producers are also well on track with the Groundwater Protection Rule on fertilizer application.”

So far, Jordahl Redlin says about four percent of Minnesota farmers have gotten certification. Participation spreads mainly by word of mouth. “You can look at a map and see it: one farmer does it, then two, then three.”

Spread is slow, he says, because the changes involve trial and error. “If you decide to try no-till agriculture, the first year you’re going to have to spray (pesticides) a lot. Community knowledge takes time to build. If their dad did it and it didn’t work, they’ll remember it for generations.”

What can be done?

Both reports offer similar solutions. The NRS speaks of the need for “systemic change” and “transformative changes” and points out that measures so far have achieved about a six percent load reduction from the baseline period of 1980-1996 while a 39 percent reduction is needed. It also warns that much more public investment will be needed, “well above $1 billion dollars annually.”  Most of that state money would be used to expand participation in the certification program and other mechanisms to compensate farmers for work they do to protect the environment.

The MCEA report on drain tile recommends some systemic changes that could make a big difference.

It points out that drainage authorities are required to consider possible damage from proposed drainage projects, but currently we lack consistent methods to estimate these. More research and guidance could help authorities identify and quantify externalized costs such as streambank erosion, channel widening, and private well pollution. If these costs were incorporated into the planning, some projects might turn out to be unjustifiably expensive, which could prompt authorities to deny permits.

The report also recommends that the Environmental Quality Board should require environmental reviews of proposed drainage projects. Or it could conduct a Generic Environmental Impact Statement on how drainage systems have impacted various parts of the state.

Market-based solutions such a cap-and-trade system could be helpful: farmers could trade pollution allowances to get the best reductions for the investment.

Finally, for the most-affected areas, the state could create a permitting system similar to the municipal stormwater system that sets minimum design requirements for runoff retention, sediment reduction, and peak flow. 

It’s hard to imagine the legislature turning to these measures; it generally prefers to protect the agricultural sector from any new requirements, buying into the sentiment that “farmers are the first environmentalists” who know best how to protect the land. But the growing popularity of farmers’ markets, home gardeners turning away from chemicals, and books such as Braiding Sweetgrass by Robin Wall Kimmerer might be an indication of gradually changing attitudes. As with new farm practices, it’s a slow process.

“It’s absolutely necessary to rethink this because we’re slowly poisoning ourselves,” says Randal Hanson. He grew up in Minnesota’s prairie pothole region and has a family history of farming.  Hanson founded the University of Minnesota Duluth’s Land Lab, where students research and grow crops for the campus dining service.

“We’re going to come to a point over the next several decades—massively documented by scientists—where we’re going to burn out our landscapes, burn out our topsoil, ruin our water systems because we’ve lost our ability to look around and see what’s really happening and understand that we are part of this landscape; we’re not separate from it,” Hanson says.

Thinking of the world more holistically could gradually prompt some of those “systemic changes” the Nutrient Reduction Strategy calls for.