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The water pollution problem in Minnesota is also a manure problem

We know fertilizer is bad for our drinking water -- and for us -- but a recent report suggests we should be paying more attention to another potent source of nitrogen and phosphorus.

We know fertilizer is bad for our drinking water -- and for us -- but a recent report suggests we should be paying more attention to another potent source of nitrogen and phosphorus. Glen Stubbe, Star Tribune

The water pollution problem in Minnesota farm country is worse than we thought.

Most of the run-off pollution comes in the form of nitrogen and phosphorus, commonly found in commercial fertilizers despite their nasty effects on both water quality and human health. Between 1995 and 2018, the average nitrate contamination in Minnesota's 72 agricultural counties’ drinking water had shot up by 61 percent on average, according to the Environmental Working Group.

Another report from that organization tracked how much nitrogen and phosphorous was sold in each county as fertilizer. Then researchers mapped out nearby cattle, hog, or poultry feedlots, where animals are confined and fattened for food. The reason: Besides fertilizer, there was another notable source of nitrogen and phosphorus seeping into the nearby fields.

And that would be… well… shit.

Minnesota has nearly 24,000 feedlots for chickens, cows, and pigs, most of them packed into the southern and central regions of the state. Together, the researchers say, they produce an estimated 49 million tons of manure each year, which is the equivalent of the waste from 95 million people -- roughly 17 times more than the number of humans who actually live here.

And when you combine that manure on top of all the fertilizer used, it really starts to add up.

In 69 of these 72 farming counties, the amount of nitrogen in fertilizer combined with the amount of nitrogen in manure exceeded the recommendations set by the Minnesota Pollution Control Agency. In 13, the combined total surpassed that recommendation by more than half. In nine, the sheer amount of phosphorus found in manure added at least 10 pounds per acre more than what the area’s crops needed.

Martin County had the most excess nitrogen, with 14,000 tons of the stuff over the limit in fertilizer (107 percent of the recommended load) and manure (69 percent of the recommended load) combined.

Also well beyond their recommended levels were Stearns County (12,500 tons), Fillmore (7,600 tons), Goodhue (7,200), and Rock Counties (6,800.)

The counties with the highest risk of phosphorus overload, based on excess pounds per acre, were Morrison (25 pounds per acre), Todd (19 pounds per acre), Kandiyohi (19 pounds per acre), Stearns again (18 pounds per acre), and Winona (16 pounds per acre).

The point, researchers say, is that our state’s extraordinary livestock expansion over the years has had a huge impact on our water supply. The Minnesota Pollution Control Agency estimates over half of Minnesota’s surface waters don’t meet basic water quality standards. Non-point source pollution --like the stuff we get from raising crops and livestock -- is responsible for some 85 percent of that pollution.

As the report notes, just because fertilizer is sold in one county, that doesn’t mean it’s used there. Regardless, we should still be worried about the sheer amount of fertilizer we’re using. And we’d be remiss if we didn’t count manure, too, and factor its impact into how much fertilizer is used in a given stretch of farmland.

“That data strongly suggest, however, that isn’t happening,” the study says. “Especially in areas with dense concentrations of livestock.”

Martin County, the area with the highest nitrogen glut, has 15 lakes on Minnesota’s 2020 list of nutrient-impaired water bodies. That includes Budd Lake, which the town of Fairmont, home to more than 10,000 people, uses for drinking water.