Dead Zone Puzzle

The Mississippi fatally links Midwest farmland to Gulf Coast fisheries.
How can one enterprise prosper without wiping out the other?

By Brian DeVore

image of spread from magazine

Donald Lirette lives in Louisiana's Terrebonne Parish on the Gulf of Mexico. Roughly half of the state's commercial anglers reside in the parish. So it's not surprising that Lirette has long been involved in local efforts to protect the gulf's fishery.

Even 20 years ago, it was becoming clear to Lirette that conserving such a resource would take more than making sure passing ships weren't dumping waste on spawning grounds. Lirette was fishing for shrimp, using "try nets" to see if it was worth dropping bigger nets.

"As soon as that try net would hit the deck, it would smell decomposed," the Cajun fisherman recalls. "Even the hermit crabs were dead, and nothing kills hermit crabs. I just kept traveling and traveling, and then I realized this wasn't local."

In fact, the lack of shrimp was the harbinger of a problem that has linked Minnesota's incredibly productive farming region with one of the nation's most vital fisheries. Scientists now know that excessive nitrogen is the major cause of the "dead zone," a Connecticut-sized chunk of the gulf that is hypoxic--containing too little oxygen to support life. They also know that, although some of that nitrogen is natural, most comes from farms.

Farming and Fishing

On a summer evening, a northeastern Iowa farmer named Dan Specht finished up hog and cattle chores, hopped into his pickup truck, and wound his way down to the nearby Mississippi River. He had fishing gear in the back, soil under his fingernails, and his farm's nutrient cycle on his mind. Specht, who's been farming and fishing near the Mississippi River community of McGregor, Iowa, for almost 30 years, doesn't feel good knowing that contaminants from his ridgetop land may be asphyxiating fish in the gulf. Part of Specht's concern is based on a big-picture view of the effect he is having on downstream neighbors. As a guest of an environmental group called the Mississippi Riverwise Partnership, Specht has visited the gulf and met with members of the commercial fishing community. "It's really fragile," he said of the area where the Mississippi meets the gulf. "It's vast, but it's fragile."

It's clear Specht is concerned about the local effects of his farming as well. He pulled into a boat landing and met up with frequent fishing partner and fellow farmer Jeff Klinge. While Klinge guided a small outboard through the backwaters, the two farmers pointed out the natural beauty of the area and talked passionately about fishing. A bald eagle soared overhead, and massive barges plied their way up and down the main channel as the men trolled for walleyes. Specht and Klinge talked about the results of a long-running study called the Big Spring Basin Demonstration Project, which has shown that nitrate-nitrogen is contaminating drinking water in the area, posing a serious health risk to infants. Like the gulf, this region is vast and fragile too.


Bacteria in the soil convert nitrogen, a rich plant nutrient, to nitrate. Nitrate-nitrogen reaches our waterways and groundwater by leaching through the soil. Some of that nitrate-nitrogen is hitching a ride on the Mississippi River and causing a supergrowth of algae when it hits the salty water of the gulf. Eventually, the algae die and sink to the bottom. The bacteria that decompose the algae consume oxygen at an extraordinary rate, particularly close to the bottom. In the depths of summer, this produces a zone so low in oxygen that fish flee. Clams, oysters, and other crustaceans that can't flee may die.

In the early 1980s, shrimp catches dropped dramatically in areas where bottom waters were hypoxic. Now, in the hardest hit areas, a boat hauling a 40-foot net for six hours might not catch a single shrimp. The size of the zone can fluctuate greatly from year to year.

Such news has prompted an official of one farm group to call the dead zone the "spotted owl" of Midwestern agriculture. No wonder: Nitrogen is a linchpin fertilizer for corn farmers, and animal manure is full of the nutrient. Overall, about half of the nitrogen that makes it to the gulf is from commercial fertilizer, and 15 percent is from livestock manure. The rest comes from human sewage, industrial point sources, and rainfall, say U.S. Geological Survey scientists.

Now, it's become increasingly clear how difficult it will be to solve a problem that has its origins in a river system's headwaters, but its biggest impacts at its mouth. The dead zone issue pits the livelihoods of two regions against each other. The Mississippi drains an agricultural region that generates 52 percent of all U.S. farm receipts--$98 billion annually--from 52 percent of the nation's farms. The Louisiana coast has 40 percent of this country's fisheries, a $2.8-billion-a-year business.

Meanwhile, Upstream

Southern Minnesota, most of Iowa, and parts of Illinois and Indiana are by far the biggest contributors of nitrogen to the gulf. In fact, the upper Mississippi River basin (upstream from the Missouri River) makes up 15 percent of the drainage basin but contributes more than half of the nitrate-nitrogen discharged to the gulf. The reason is simple: More corn and soybeans are grown in the Midwest than anywhere else in the country. Corn needs a lot of nitrogen fertilizer to grow. As a legume, the soybean captures nitrogen from the air. Nitrogen leaching is part and parcel of these cropping systems.

Researchers at the Southwest Minnesota Research and Outreach Center near Lamberton have put together a series of historical charts that show how a two-crop system of corn and soybeans has replaced a system that, at the turn of the century, included wheat, oats, barley, rye, alfalfa, and pasture. Ninety-one percent of the cropped acreage in a nine-county area of Minnesota is now planted to either corn or soybeans. This pattern has been repeated in other Midwestern states.

Since 1973 University of Minnesota soil scientist Gyles Randall has been tracking nitrate-nitrogen levels in drainage tile lines running under southern Minnesota farm fields. He has found that nitrogen losses from corn and soybean fields can be 30 to 50 times higher than from land planted to perennial plant systems such as hay or grass. As corn and soybeans have replaced pasture, hay, and small grains, nitrate-nitrogen levels in the water have risen. Meanwhile, the amount of nitrate-nitrogen entering the gulf has more than doubled during the past four decades.

If nitrogen is the substance that's killing the gulf, artificial drainage is the hypodermic syringe mainlining it into the nation's aquatic arteries. Natural drainage systems, such as prairie potholes and wetlands, can hold 40 to 90 percent of the nitrogen that runs off a field, according to the Bill Mitsch, wetland ecologist at Ohio State University. Artificial drainage sends water directly into rivers, eliminating opportunities for nutrients to be captured by vegetation and soil. University of Minnesota soil scientist David Mulla says, "Tile drainage is one of the most important mechanisms for transfer of nitrate-nitrogen to the Mississippi basin."

Federal environmental officials are quite aware of the role Midwestern nitrogen plays in creating the dead zone. In January the U.S. Environmental Protection Agency presented Congress an "action plan" for resuscitating the gulf by 2015. The proposed $15 billion plan calls for funding research that tracks the flow of nitrogen in the basin. It would also support incentive-based programs for getting farmers and other landowners to reduce the amount of nitrogen they send south by 30 percent.

One voluntary program that is already proving popular among Minnesota farmers is the Conservation Reserve Enhancement Program, which converts erosion-prone cropland to other vegetation such as grassland. Grasslands hold soil and slow runoff. CREP allows Minnesota to match federal funds for putting conservation easements on up to 100,000 acres in the 37-county Minnesota River Valley.

As of mid-spring, 1,029 CREP easements had been recorded in the basin, covering a total of 38,883 acres. These acres are flood-prone and don't produce a crop many years anyway. CREP gives farmers and other landowners an incentive to allow water to take its time getting to the river.

Razor-Thin Margin

Only so many nitrogen-trapping wetlands will be tolerated in a region as thoroughly farmed and drained as southern Minnesota. Crop production has razor-thin profit margins, and setting aside even a few acres for the benefit of "natural drainage" is seen by many farmers as a major economic burden.

On-farm research in Minnesota and other Corn Belt states shows that farmers can reduce nitrogen fertilizer rates significantly without sacrificing yields. Increasingly, farmers are using soil tests and more precise application to reduce the amount of excess nutrients that end up in soil, and eventually water.

Specht is proof of how creative farmers can be at keeping nutrients where they belong while still maintaining a productive farming operation. For one thing, he doesn't always assume that raising corn and soybeans is his only option. Specht produces beef on his steepest ground, using management-intensive rotational grazing. This system, which consists of moving livestock based on how fast the pasture grows, is a way to make soil- and water-holding perennial plant systems profitable, according to research conducted in Minnesota, Iowa, and Wisconsin. Moreover, the cattle spread manure at a rate the plant system can use. By putting his hillsides to work supporting livestock, Specht doesn't have to raise corn and soybeans on his most erodible acres.

On the rest of his farm, Specht uses a mix of rotation schemes and cover crops. For example, he may sow oats in early spring. By the time he is ready to disc the land and plant corn, the soil is covered with a thick growth of oat plants, which are very effective at protecting soil that otherwise would have been bare in early spring.

Specht also plants rye in the fall after harvest. By the time the snow melts the following spring, he has a lush, green ground cover that suppresses weeds. Livestock is an essential part of the equation, justifying the production of oats, alfalfa, and pasture grasses.

The result of all this effort? A soil surface protected by green vegetation throughout much of the growing season. These plants soak up nitrogen as they grow and create a soil structure that slows and reduces runoff. A visit to the steepest part of the farm soon after a rainstorm seems to support this conclusion: While Specht's fields are intact, silt from a neighbor's cornfield is caked against a fence--even though the neighbor is using commonly accepted conservation practices such as contours and terracing.

A Public Good

Diverse farming systems are the key to maintaining long-term environmental health here in the Midwest (as well as the Gulf of Mexico), say an increasing number of scientists, including David Tilman, University of Minnesota ecologist. Tilman, who has conducted extensive studies on grass-based ecosystems, maintains that diversity should be considered a public good because of the resiliency it provides the environment. And, he argues, that means society needs to find a way to support diverse farming operations.

However, right now the federal crop subsidy system pays farmers for planting corn and soybeans, and penalizes them for diverse rotations that include small grains, pasture, and hay. Despite the advantages to Specht's methods--his input costs are a fraction of what they once were, and his soybeans recently won a local yield contest--his system can be management- and labor-intensive. Specht is rewarded somewhat in the marketplace because his soybeans, beef, and hogs qualify for organic premium prices. But those markets are still fragile, and he has little financial incentive to mind his nutrient cycle as closely as he does.

Specht worries that the government's gulf action plan will provide cost-share monies only for farmers raising corn and soybeans to install terraces and grassy buffer strips. Such structures will do little to reduce nitrogen leaching if the tile lines running underneath them are contaminated. "You are not going to have an effect on nitrate levels in drainage water until you change the farming practices on the fields it's draining," says Specht.

Randall, the University of Minnesota soil scientist, thinks "best management practices" such as more precise fertilizer application rates and timing will help reduce nitrate-nitrogen leaching, but wonders if that will be enough. "The question is whether these practices will be sufficient to reduce nitrate losses to meet the environmental goals of society."

Indeed, who knows what society's goals really are when it comes to the gulf dead zone? The EPA action plan says reducing the amount of nitrogen and other nutrients that enter the gulf by 30 percent will result in only a partial recovery of the fisheries. The agribusiness community maintains that measures that cut nutrient loading in the Mississippi basin by more than 30 percent could cripple farming in the Midwest and send corn and soybean production to other parts of the country or overseas.

Down on the bayou, Donald Lirette isn't waiting passively for Midwestern agriculture to cork its leaky nutrient cycle. His home state has certainly played a role in trashing aquatic systems, and Lirette and others are working to reclaim sick estuaries. But the veteran waterman knows that upstream problems can quickly wipe out downstream solutions.

"I've been to Iowa and Minnesota. All I ever saw was cornfields and hogs, and I know all those things have runoff," he says. "But we're guilty too. This is a good exercise in trying to get people to work together.

For information on diverse farming systems that can reduce nutrient leaching, log onto, or call 651-653-0618.

For information on keeping nutrients from escaping your home lawn, call your local University of Minnesota Extension Service office and ask about the 12-part Sustainable Lawn Care Information Series, or log onto

The Science Museum of Minnesota has a display and kid-oriented web site devoted to the Gulf of Mexico's dead zone:

Brian DeVore, Minneapolis, is Editor of the Land Stewardship Letter, published by the Minnesota-based Land Stewardship Project.