Farm runoff may cause largest Dead Zone yet


Photo by Joe Germuska, Flickr

Iowa is one of nine states along the Mississippi River implicated in contributing to what is expected to be the largest dead zone ever in the Gulf of Mexico.

The New York Times reports that phosphorous and nitrogen from fertilizers and animal waste runoff are largely to blame for the dead zones. The recent flooding along the Mississippi has exacerbated this runoff. With this impending damage to the Gulf, environmentalists are calling for stricter regulations of farms near the Mississippi:

For years, environmentalists and advocates for a cleaner gulf have been calling for federal action in the form of regulation. Since 1998, the Environmental Protection Agency has been encouraging all states to place hard and fast numerical limits on the amount of those chemicals allowed in local waterways. Yet of the nine key farm states that feed the dead zone, only two, Illinois and Indiana, have acted, and only to cover lakes, not the rivers or streams that merge into the Mississippi.

Many of the farmers along the Mississippi fear that the EPA will indeed heed the call and set chemical limits.

Don Parish, senior director of regulatory relations for the American Farm Bureau Federation, a trade group, says behind that policy is the faulty assumption that farmers fertilize too much or too casually. Since 1980, he said, farmers have increased corn yields by 80 percent while at the same time reducing their nitrate use by 4 percent through precision farming.

“We are on the razor’s edge,” Mr. Parish said. “When you get to the point where you are taking more from the soil than you are putting in, then you have to worry about productivity.”

One argument for Iowa farmers in particular against EPA regulation is that the limitations of their land are responsible for much of the runoff, not excessive use of chemicals. However, many experts believe that Iowa’s land isn’t the problem, but instead just adds to the problem.

John Downing, a biogeochemist and limnologist at Iowa State University, said structural issues were also to blame. Many farms in Iowa, he said, are built on former wetlands and have drains right under the crop roots that whisk water away before soils can absorb and hold on to at least some of the fertilizer.

Still, overapplication of fertilizers remains a key contributor, he said. “For farmers, the consequences of applying too little is much riskier than putting too much on.”

The Iowa Environmental Focus covered the Dead Zone in our radio program.  To listen to the piece or read the transcript, click here.

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