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'Dead zones' threaten fisheries

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Still, scientists say it takes time for a rise in fertilizer use to harm coastal ecosystems. In a 2002 study, Howarth and other scientists found that falling levels of dissolved oxygen in coastal waters lagged 10 to 20 years behind increased chemical fertilizer use beginning in the 1940s. That lag effect is worrisome, he says, because fertilizer use has more than quadrupled globally since 1960.

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The use of nitrogen has increased, too. Nitrogen fertilizers were 37 percent of all fertilizers used in 1961, but grew to 60 percent by 2001, according to Fertilizer Institute data. "If you look globally at what humans are doing to the nitrogen cycle, we're increasingly making nitrogen available to the environment," Dr. Howarth says. "Almost 75 percent of the increase is through fertilizers."

The fertilizer industry in the US has been working with farmers to reduce fertilizer overuse and resulting runoff since the 1960s. But pressure from the Environmental Protection Agency in the '90s also has pushed the industry toward new technologies. Global positioning satellite technology, linked to fertilizer applicators on tractors, permits "precision farming" in which each acre gets specific chemicals according to its soil condition.

"Applying more won't necessarily get more crop, and farmers understand that it's not good for their bottom line," says Rino Maddalena of the Fertilizer Institute in Washington D.C.

Even so, several farm authorities say it is not uncommon for farmers to use more nitrogen and other fertilizers than they need as a modest insurance policy. Better to slightly overfertilize than underfertilize and underproduce, the thinking goes.

To address this concern, the American Farmland Trust (AFT), a nonprofit group that attempts to protect cropland, has developed a new form of crop insurance. The risk-management program encourages farmers to apply less nitrogen fertilizer. In this scheme, a farmer agrees to use a lesser amount of nitrogen fertilizer, based on nutrient management advice. If the farmer's output falls below the output of a test plot on his land that has the maximum nitrogen fertilizer applied to it, then he receives the difference in cash.

So far, 27 pilot projects are under way in Minnesota, Wisconsin, Ohio, and Illinois, says Brian Brandt of the AFT's Agricultural Conservation Innovation Center. In three years, the project has seen a 24 percent reduction in nitrogen use among the farmers. Only a handful saw yields fall. They were paid the difference, about $6 per acre.

It pays to use less

One participant, Burley Hall, a farmer with 2,100 acres north of Urbana, Ohio, now uses some 35 pounds less nitrogen per acre of corn - a reduction of more than 20 percent. That reduction saves him money. And once, when his crop came in a fraction of a bushel less than his test strip, he got reimbursed $900. But his enthusiasm for the program runs deeper than economics.

"We've got creeks that run through our land," Mr. Hall says. "We live here and drink the water. If I'm buying this stuff [nitrogen], I don't want to see how far down the stream I can run it. You've got to watch out for the environment by all means and this is one way of doing it."

One high-tech idea in the works would take another big whack at nitrogen use - but from the other end of the equation. Arcadia Biosciences in Davis, Calif., is working to make corn and other plants more efficient users of nitrogen already in the soil. For example, using genetic engineering, it has modified canola with a gene found in barley. The effect is to activate the plant's roots to absorb nitrogen more aggressively than before.

"We've grown the same yield as a conventional crop of canola using less than half as much nitrogen," says Eric Rey, the firm's president.

Arcadia has conducted three years of tests for the US Department of Agriculture. But the first commercial canola and rice seeds won't be ready until 2008 or 2009, Mr. Rey says. He acknowledges, too, current concerns over genetic engineering. On the other hand, farmers cut costs and use less fertilizer, he adds. "So the environment is improved by farmers making more money."