Tiles, Farms and the Dead Zone

By Editorial, New York Times
20 October 2010

Every year, usually beginning in late spring, an oxygen-depleted dead zone forms in the Gulf of Mexico at the Mississippi River’s mouth, killing off fish, shrimp and other marine life. By the time cooler weather restores life to the zone, the fishing industry has sustained substantial losses.

Scientists have long known that the dead zone — this year it covered 7,000 square miles — is created largely by nitrate washed downstream from fertilized fields as far north as Minnesota. A study in the Journal of Environmental Quality by scientists from Cornell University and the University of Illinois has now conclusively identified the largest source of that nitrate: tiled farm fields.

For as long as farmers have been farming in the Midwest, they have been laying drainage tile — often perforated plastic tubes installed 2 feet to 4 feet below the surface — to drain wetlands and create arable fields in places that would normally hold standing water. The problem is that the system also sluices away nitrogen fertilizer, which eventually flows through tributaries into the Mississippi and ends in the Gulf of Mexico.

Mark David, a University of Illinois researcher, observed that “farmers are not to blame.” We agree. Tiling is as old as Midwestern farming. What’s needed now is more research and direct incentives from the Agriculture Department to find ways to mitigate this problem.

These include: restoring wetlands, where possible; growing cover crops to absorb water in the spring, when runoff is heaviest; different methods of applying fertilizer; and even methods of treating the runoff before it reaches creeks and rivers. Sacrificing life in the gulf for corn in the fields is a trade-off that has to stop.