Corn and the Growth of the Gulf Dead Zone

Washing off farms and yards, nitrate is largely respon­si­ble for the Gulf of Mexico’s infa­mous “dead zone.” Nitrate and other nutri­ents from the vast Mississippi River basin fun­nel into the Gulf, suck­ing oxy­gen out of the water and killing almost every­thing in their path.

The pol­lu­tion is one of America’s most wide­spread, costly and chal­leng­ing envi­ron­men­tal prob­lems, accord­ing to the U.S. Environmental Protection Agency. Sewage treat­ment plants along the rivers already have spent bil­lions of dol­lars, and some farm­ers now use com­put­ers to apply fer­til­izer with pin­point precision.

But after three decades of exten­sive efforts to clean it up, nitrate along the rivers is get­ting worse. In Hermann, the lev­els have increased 75 per­cent since 1980, accord­ing to U.S. Geological Survey research pub­lished last year.

The pol­lu­tant con­tin­ues to pour into the rivers, and ulti­mately the Gulf, at a grow­ing pace. And no one—at least yet—has fig­ured out exactly why.

1,247 miles downstream

Hermann is an ideal place to start unrav­el­ing the mys­tery. There are no big fac­to­ries here, no major sewage treat­ment plants, and not even much of the inten­sive row-crop agri­cul­ture some­times blamed for heavy runoff. Rather, this small city looks like some­thing out of a German fairy tale. Churches, shops and red-brick houses line tidy streets. Vineyards dot the rolling hills. Tourists arrive via Amtrak train to hear oom-pah bands at Oktoberfest and dine on bratwurst with sauerkraut.

How could Hermann be respon­si­ble for increas­ing the pol­lu­tion that cre­ates a dead zone 1,247 miles downstream?

The answer is Hermann is merely a micro­cosm of an immense prob­lem involv­ing 31 states and more than 76 mil­lion people.

Hermann sits roughly in the cen­ter of the vast Mississippi River basin, which drains 1.24 mil­lion square miles stretch­ing from the Rockies to the Appalachians.

The Missouri River, as it rushes past Hermann’s churches and shops, car­ries the residue of life upstream. Rain washes excess nitro­gen and phos­pho­rus, along with other pol­lu­tants, from farm­ers’ fields, cities, fac­to­ries, cars and sub­ur­ban lawns into ditches, streams and trib­u­taries, and finally to the river itself. The “Big Muddy” joins the mighty Mississippi just north of St. Louis, then makes a sharp right turn and rushes past the soar­ing St. Louis Arch on its way to the sea off Louisiana. 

When the nutrient-rich water emp­ties into the Gulf far down­stream, it trig­gers a bio­log­i­cal phe­nom­e­non with deadly results. The nutri­ents serve as an all-you-can-eat buf­fet for hun­gry algae. The phy­to­plank­ton pop­u­la­tion booms and then dies, sink­ing to the bot­tom, where bac­te­ria decom­pose the organ­isms and use up pre­cious oxy­gen in the process. The result­ing low-oxygen environment—also called hypoxia—is so toxic that all ani­mals must flee or die.

Hypoxia dri­ves away shrimp, crabs and fish and kills crea­tures such as worms at the bot­tom of food chains.

“There is die-off, a loss of ecosys­tem diver­sity,” said Nancy Rabalais, a marine ecol­o­gist and direc­tor of the Louisiana Universities Marine Consortium in Chauvin, La. “If you have con­tin­u­ous year-after-year hypoxia, some ani­mals won’t be able to recruit back into the area.”

Rabalais has been map­ping hypoxia for almost 30 years. Her research helped spawn a state/federal task force, which set a goal of cut­ting the Gulf’s dead zone almost in half, to about 1,930 square miles, by 2015.

Yet the dead zone keeps grow­ing fat­ter, like an obese patient unable to shed weight. Last year it was 6,800 square miles—more than triple the goal.

“We’re a long way from the tar­get now—a very long way,” she said. “When that tar­get was set, it didn’t seem impos­si­ble, but it’s just get­ting harder and harder.”

In addi­tion to the 75 per­cent increase at Hermann, nitrate lev­els have increased 76 per­cent since 1980 along the upper Mississippi River at Clinton, Iowa, accord­ing to the USGS research. In all, nitrate runoff in the entire basin increased 9 per­cent over the past 30 years, and much of that increase came from the water­shed upstream of Hermann and Clinton.

“This the first time any­one has been able to show the actual con­cen­tra­tions have either not changed or actu­ally increased when we’re sup­posed to be reduc­ing the loads,” said Don Scavia, a pro­fes­sor of envi­ron­men­tal sus­tain­abil­ity at the University of Michigan in Ann Arbor who stud­ies the dead zone.

“Whatever con­ser­va­tion prac­tices have been put in place are not enough,” he said.

The corn theory

One the­ory is that more fer­til­izer is wash­ing into the water­shed because corn acreage has sky­rock­eted. But urban runoff, live­stock and other sources could play a role, too.“These are really large water­sheds with a lot of things happening—changes in crop pat­terns, live­stock use, human pop­u­la­tion,” said Lori Sprague, a USGS hydrol­o­gist based in Denver who was lead author of the nitrate study. “All of those things change water quality.”

Farm fer­til­izer and live­stock manure are the two biggest sources of total nitro­gen in the Missouri River water­shed, together respon­si­ble for 70 per­cent, accord­ing to 2011 USGS data. A 2008 study of the entire Mississippi River water­shed had sim­i­lar find­ings, with agri­cul­ture con­tribut­ing 70 per­cent of the nitro­gen and phos­pho­rous that ended up in the Gulf. Scientists in 2009 also reported a direct cor­re­la­tion between inten­sive crop pro­duc­tion, par­tic­u­larly corn, and nitrate-nitrogen lev­els in rivers.

Nationally, con­sump­tion of nitro­gen fer­til­izer has tripled since the 1960s, surg­ing to 12.3 mil­lion tons in 2010, accord­ing to USDA data. The amount of nitro­gen applied as farm fer­til­izer grew 18 per­cent between 1987 and 1997, accord­ing to a 2006 USGS study.

It sounds clear-cut. Many farm­ers, how­ever, tell a dif­fer­ent story.

In the Bootheel area of south­ern Missouri, farmer Mike Geske grows about 2,000 acres of corn, cot­ton, rice and soy­beans near Matthews, Mo. The land lies flat as a plate, the north­ern­most reaches of the fer­tile Mississippi delta.

Geske, a third-generation farmer, said when he first started farm­ing in the 1970s, he would lay a thick dose of fer­til­izer on his fields in the spring. “Anhydrous ammo­nia was so cheap, we put on 80 to100 pounds extra,” he said.

Today, he applies fer­til­izer three or four times through­out the year so plants can use it as they need it. He said he uses 20 to 25 per­cent less fer­til­izer these days, yet he gets 25 to 30 per­cent more bushels of corn per acre. He cred­its bet­ter seed tech­nol­ogy and care­ful man­age­ment of nutri­ents in the soil.

Farther upstream, fourth-generation farmer Ron Hardecke raises crops, hogs and cat­tle on 2,000 acres in Owensville, Mo., about 35 miles south of Hermann. He said he care­fully mon­i­tors his nitro­gen use.

“Sometimes it’s por­trayed we’re out here dump­ing fer­til­izer for fun,” he said. “But if you pay the bill, why, you don’t use more than you need.”

Nationwide, farm­ers are get­ting more grain out of their fer­til­izer, accord­ing to the National Corn Growers Association. Nitrogen use has decreased 38 per­cent in terms of pounds per bushel of corn, said Rod Snyder, direc­tor of pub­lic pol­icy for the trade group.

Nevertheless, corn farm­ers are using as much fer­til­izer per acre as ever on their high-yielding crops, accord­ing to fed­eral data. On aver­age, farm­ers applied 58 pounds of nitro­gen per acre to corn crops in 1964. By 1985, that num­ber had grown to 140 pounds per acre, where it remained in 2010.

In addi­tion, more acreage is being planted as corn prices boom, accord­ing to U.S. Department of Agriculture data. In 2012, farm­ers planted 96 mil­lion acres of corn—the high­est level in nearly 70 years, and up nearly 22 per­cent from a decade earlier.

“The pri­mary cause [of nitrate pol­lu­tion] is row crop agri­cul­ture, and the pri­mary cul­prit of that is corn.

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