Growing corn in the Midwest for green fuel could increase pollution downriver and contribute to a "dead zone" that forms each summer in the Gulf of Mexico, a national agriculture expert said Tuesday.

"We're in a dilemma in this country," Gary Mast, of the U.S. Department of Agriculture said Tuesday. "We want food. We want fuel. We want it to be produced environmentally soundly."

The problem is that corn needs more nitrogen fertilizer than other crops. More corn means more nitrogen fertilizer. Runoff carrying the fertilizer fuels the growth of microscopic organisms that then die, fall to the bottom and decompose, using up the oxygen there.

Mast is a Department of Agriculture representative on a national task force created in late 1997 to find ways to reduce the runoff of nutrients. He said farmers have put in 2.3 million acres of buffer zones to absorb farmland runoff before it gets to waterways.

He added that 1.4. million acres of wetlands have been added to the Mississippi River basin, including at least part of 30 states.

It doesn't compensate for all of the additional acres in corn, he said in an interview, but "I think we've made progress."

He summarized the problem earlier to the Mississippi River & Gulf of Mexico Watershed Nutrient Task Force, which environmentalists and others criticized during a public comment period for failing to do much of anything.

The dead zone has averaged about 4,800 square miles since 1990. The record, 8,500 square miles, was in 2002. Last year's covered about 6,662 square miles — about the size of Connecticut and Rhode Island together. The area may rise 30 feet or more above the bottom. Within it, nothing lives. There's not enough oxygen to sustain life.

Matt Rota, water resources program director of the Gulf Restoration Network, is among those who say the task force hasn't done enough. "I definitely support getting off of oil," but letting more fertilizer wash down the Mississippi River would be robbing Peter to pay Paul, he said.

"Our economy in that basin is totally dependent on natural resources," said Tracy Kuhns of Louisiana Bayoukeeper, a coalition of charter and commercial fishing captains and coastal tourism and restoration groups.

She said she first heard about the dead zone 13 years ago, when a commercial fisherman "asked why so much money and time was being put into protecting turtles when there's this giant dead zone in the Gulf of Mexico."

In the years since, she said, "We hear talk about it. We hear that we're doing studies. You know, it's just going on and on and on and on and nothing seems to be happening."