As public works director for the city of Hastings, Nick Egger knows the cost of protecting drinking water from farm chemicals.

The Mississippi River town already had to foot the bill for one $3 million water-treatment plant to remove nitrate from its drinking supply, and it has two more wells polluted by the fertilizer byproduct. But city officials like him have had no authority to change local farming practices, Egger said, other than to "ask politely."

Now, with a landmark state regulation of nitrogen fertilizer set to take effect, he's hoping he'll finally get help. It's a bold move for the state Department of Agriculture, and Minnesota's first stab at directly regulating the application of commercial nitrogen fertilizer on row crops. Minnesota farmers apply about 700,000 tons of commercial nitrogen fertilizer to their fields each year, primarily to boost corn yields, and it leaches into groundwater, as well as lakes and streams.

"They know that this is quite a problem for public water suppliers," Egger said.

Years in the making, the final Groundwater Protection Rule was signed by state Agriculture Commissioner Thom Petersen on May 28 and is now on the desk of Gov. Tim Walz. It bars farmers from applying nitrogen fertilizer in certain seasons in certain parts of the state and regulates application in 30 areas, such as Hastings, where community water supplies show high nitrate levels.

Drinking water above the state and federal nitrate health limit — 10 milligrams per liter — is a particular risk to infants and pregnant women. Infants can develop a condition known as blue baby syndrome from lack of oxygen. In adults, nitrates have been linked to health effects such as increased heart rates and, potentially, cancer.

The state's surface waters are also at risk, although they are not part of the new rule. More than one quarter of the lakes, streams and wetlands in Minnesota now show nitrate levels above the 10 milligrams level. Excess nitrate causes toxic algae blooms and depletes oxygen, killing fish.

Farmers OK with it

State health and agriculture officials say they're confident the hard-fought compromise will improve drinking water quality in Minnesota's hardest hit areas, and it appears to put Minnesota at the forefront of states moving to regulate farm application of nitrogen, a problem in many farm states.

"I think we ended up with a common-sense rule that will get us to clean drinking water levels while still allowing farmers to make a profit," said Susan Stokes, assistant agriculture commissioner.

Results, in the form of cleaner water, will take about five years, said Sandeep Burman, manager of Drinking Water Protection for the Minnesota Department of Health.

Farmers generally expressed acceptance.

"The soil can only hold so much nitrogen," said Brent Nyquist, a Cokato farmer who was struggling to plant soybeans in wet fields last week.

Kirby Hettver, board chairman at the Minnesota Corn Growers Association, said the vast majority of farmers already use best-management practices and don't apply nitrogen in the fall in sensitive areas. But he called the final rule "reasonable," and said it smartly targets hot spots. Only a fraction of Minnesota farmers will be affected. Just 13% of the state's cropland is covered by the new rule, and it doesn't cover manure application or private wells.

"We're always looking to do things better," Hettver said.

Other groups, however, criticized the measure as too narrow and too reliant on voluntary farming practices.

Gyles Randall, a retired University of Minnesota soils scientist and an authority on nitrogen application, said he's deeply disappointed.

"After 20 years there won't be any improvement in nitrate in the water," he said.

Randall said the rule is too focused on when farmers apply fertilizer, as opposed to how much. "They went after the wrong thing," Randall said.

Randall said Agriculture Department surveys show that Minnesota farmers routinely overapply commercial nitrogen — about 100,000 tons too much each year — not counting the tons of manure they also spread on fields.

Trevor Russell, water program director at Friends of the Mississippi River, was a shade more optimistic. He described the final rule as a "timid" step for water quality but "a giant step for the Minnesota Department of Agriculture."

"This is the first time this state has exercised its regulatory authority over cropland agriculture for water quality purposes," Russell said.

Steve Morse was a legislator in 1989 when he co-authored Minnesota's Groundwater Protection Act. Today he runs the Minnesota Environmental Partnership and said he thinks it's appalling that it's taken 30 years to get regulation to address nitrate contamination.

"It's kind of like a slow-motion Flint water crisis."

What about private wells?

The new rule prohibits applying commercial nitrogen in the fall or on frozen fields in areas with vulnerable soil — coarse textured soils, karst geology or shallow bedrock — and on farmland within one of 30 Drinking Water Supply Management Areas where the nitrate level is at or above 5.4 milligrams per liter.

The rule also creates a tiered regulatory program for fertilizer in those drinking-water hot zones, although it relies heavily on encouraging best management practices developed by the University of Minnesota. One of the first steps is to recruit local advisory teams to work with individual farmers to achieve compliance.

"We have to give all farmers the opportunity to try the voluntary measures and see if they work," Stokes said.

The fall and frozen field ban starts in 2020. The scrutiny of fertilizer application in the drinking water zones really won't start for at least three years, Stokes said.

Jeff Broberg, a geologist near Rochester who runs the Minnesota Well Owners Organization, decried the lack of protections for private wells, which he said supply about a quarter of Minnesotans. There are townships where more than 40% of the private wells are at or over the nitrate limit, records show. Broberg himself hauls his drinking water in jugs from a friend's house because his well is so contaminated.

"It's leaving out the people that are the most impacted," said Broberg.

Even as the rule takes effect, the conversation has turned to more ambitious solutions to close the nitrogen spigot. A growing number of researchers, rural water managers and conservationists say the key is diversifying what Minnesota farmers grow, beyond corn and soybeans, and keeping fields planted year-round to sequester carbon and minimize runoff.

"There's no model that shows we can get anywhere near our state's water quality goals [while] growing primarily annual row crops like corn and soybeans that require extensive tillage, drainage and fertilization," said Russell at the Friends of the Mississippi River. "Even the best-performing corn and soybean rotation will contribute nitrate to surface water and groundwater. Period."

Jennifer Bjorhus • 612-673-4683