The Star Tribune has unlocked reporter Josephine Marcotty’s article from last weekend on how agricultural runoff is poisoning much of Minnesota’s drinking water.

The biggest problem: nitrate contamination from the huge amount of fertilizers (including hog manure) that get dumped on the state’s farmlands each year. Nitrates have been linked to cancer as well as to a potentially fatal blood disorder in infants called methemoglobinemia, or “blue baby syndrome.”

Writes Marcotty:

At the State Capitol and in town halls across the state, there is growing urgency to confront the problem. Thousands of private wells have been found to exceed state health limits for nitrates, and some communities have spent millions on filtration systems to clean their drinking water.

After four decades of progress against pollution from factories and cities, environmentalists say, Minnesota cannot take the next step in preserving its lakes and rivers without addressing one of the last, biggest sources of pollution: agriculture.

Unless farm runoff is vastly reduced — and soon — environmentalists say the state may never reclaim its heritage as the land of sky-blue waters.

Right now, farmers are not required by law to limit their pollution, Marcotty reports. There are voluntary guidelines in place, but environmentalists believe those guidelines aren’t working fast enough.

“A state Department of Agriculture survey of 52,000 wells found that 10 percent exceed health limits for nitrates, and the rate is higher in agricultural areas,” reports Marcotty. “But the estimate could be low: About half the well owners said they never tested their wells.”

Agricultural groups claim there’s no proof that farmers are to blame for most of the contaminated wells. Nor are they — and some others — convinced that new regulations are necessary.

So, as clean water activitists work for tighter laws, renewed efforts are being made to persuade farmers — and other landowners — to voluntarily reduce their nitrogen load on the land. But many environmentalists are skeptical that such efforts will work. One is Jeff Broberg, a geologist and clean water activist whose own tap water in his home near Lewiston in southeastern Minnesota is now undrinkable because of nitrate poisoning.

Voluntary efforts may be well and good, he told Marcotty, “but I am dubious.”

You can read Marcotty’s article here.