How do we fix Iowa’s nitrate pollution?

How do we fix Iowa’s nitrate pollution?

A network of tiles running under 12 million acres of rich Iowa soil has transformed once swampy lands into some of the nation’s most productive farmland.

But the same underground drainage system that has turned the state into an agricultural powerhouse is also being blamed for environmental problems that the state’s settlers couldn’t have imagined when they dug the first tiles more than a 100 years ago.

Scientists say the tiles funnel tens of thousands of tons of nitrates — as well as dissolved phosphorus — into Iowa’s waterways each year. As a result, cities such as Des Moines struggle to remove the nutrients to make their drinking water safe.

Combined with intensive cropping and fertilizer use, the tiles create “a perfect situation for leaching high concentrations of nitrates” into Iowa waterways, said Susan Heathcote, water program director at the Iowa Environmental Council.

Now, Iowa is experimenting with ways to stem the release of those nutrients, incorporating nitrate-absorbing wetlands and other practices with tiling to cut levels that threaten public water systems.

It comes at a pivotal time for Iowa agriculture. The state’s century-old tiling is viewed as crumbling and too small to deal with the increasingly heavy rainfalls brought on by climate change.

Replacing it will cost as much as $6 billion over the coming decades, farm experts predict.

But if that is done without conservation in mind, environmentalists fear that an upgraded drainage network may only worsen the state’s water quality problems, potentially opening wide the faucet for more nitrates to enter rivers and streams.

“It’s not ‘yes’ or ‘no’ on whether we have drainage systems,” said Bill Northey, Iowa’s secretary of agriculture. “The question is: How do we manage those drainage systems in a way so we have less impact from nitrates.”