Curbing Nitrogen Pollution

Across the country, forests, streams and coastlines are getting extra doses of nutrients containing the element nitrogen. Researchers say the long-term impact of these unwanted compounds on the environment could be serious. The Great Lakes Radio Consortium’s Daniel Grossman reports on some efforts to reduce nitrogen pollution:


Across the country, forests, streams and coastlines are getting extra doses of nutrients
containing the element nitrogen. Researchers say the long-term impact of these unwanted compounds on the environment could be serious. The Great Lakes Radio Consortium’s Daniel Grossman reports on some efforts to reduce nitrogen pollution:

A thunderstorm soaks the land and lights the sky. The electric jolts of the lightning change nitrogen in the air into compounds needed for plants to grow. Lightning, as well as microbes in the soil, converts annually nearly 100 million tons of atmospheric nitrogen into plant nutrients. Humans make the same compounds in factories and call them fertilizer, a mainstay of agriculture. Between these synthetic chemicals and a smaller quantity of related compounds produced when fossil fuels are burned, humans produce more nitrogen-rich nutrients than nature makes on the seven continents. University of Minnesota ecologist David Tilman says such extra nutrients are a concern.

“Right now half or more of the nitrogen we put on a farm field just washes through the soil and down into the groundwater into lakes, rivers, streams and into the ocean.”

This wasted nitrogen often travels great distances causing widespread damage. Tilman says on land, the nutrients cause exotic weeds to outgrow native plants. In the ocean, the nutrients cripple critical habitats. The ecologist says nitrogen pollution must be cut. One place to start is on the farm.

“We have to find some way to grow crops where the crops take up much more of the nutrients that we apply.”

(Sound of walking through grass. Quiet bird calls in background.)

Near Chesapeake Bay, farmer and agricultural scientist Russ Brinsfield walks across a patch of tall dry grass.

We’re on the edge of a field, about a sixty-acre field of corn, on the beautiful Eastern Shore of Maryland.

This field is a research plot at the Maryland Center for Agro-Ecology. Here Brinsfield is studying agriculture’s environmental impact. Chesapeake Bay’s waters have high concentrations of farmer’s nutrients, causing blooms of the toxic algae Pfiesteria. The pollution has also caused declines in sea grass beds. Brinsfield says solutions to the problem fall into two categories.

“The first series of practices are those practices that we’ve been able to demonstrate that by a farmer implementing them he can reduce his inputs without affecting his outputs… that at the end of the year have added profit to his bottom line.”

For instance, testing the soil’s nitrogen level before fertilizing. And splitting fertilizer applications into two doses rather than one so that nutrients are added only when plants need them. Such simple measures are good for environment and the bottom line. Brinsfield says in the last 10 years most farmers on the Eastern Shore of Maryland have cut fertilizer use this way. Then there’s the other category of improvements.

“We’re going to have to do some things-ask some farmers to do some things-that may cost them more to do than what they are going to get in return from that investment.”

For example, in the winter, many fields here are fallow and bare. That means top soil erodes when it rains, taking with it residual fertilizer. It wasn’t always this way.

“I can remember my dad saying to me, ‘every field has to be green going into the winter, Son.’ So all of our fields were planted with rye or wheat or barley. It served two purposes. First, the animals grazed it. And second, it held the soil intact.”

And intact soil retains its fertilizer. Such winter cover crops also prevent fertilizer loss by storing nutrients in plant leaves and stalks. This used to be dairy country and cover crops grazed by cows made economic sense. Now farmers mostly grow grains. Planting a cover crop could cut nitrogen flow from farms by 40 percent but it costs farmers about $20/acre and provides no economic benefit to them. Brinsfield says farmers need an incentive.

“For the most part, farmers are willing to participate and to do those things that need to be done, as long as they can still squeak out a living.”

To help them squeak out a living, the state pays some farmers to sow cover crops. The state also pays them to plant buffers of grass and trees that suck up nutrients before they leave the farm. Today farms in six states that are part of the Chesapeake’s huge watershed contribute about 54 million pounds of nitrogen to the bay. The goal is to cut this figure approximately in half by two thousand and ten. Robert Howarth, a marine biologist and expert on nitrogen pollution at Cornell University, says though ambitious, this target can be achieved.

“I think most of the problems from nitrogen pollution have relatively straightforward technical fixes. So the real trick is to get the political will to institute these.”

Howarth says much of the nitrogen problem could be eliminated with a blend of government subsidies and regulations. But more will be needed as well… solutions of a more personal nature.

(sound of Redbones Barbeque)

There’s a pungent, smoky aroma in the air at Redbones Barbeque in Somerville, Massachusetts. The crowded bistro serves up a variety of ribs, chicken, sausage and other meats, dripping with savory sauces. University of Minnesota ecologist David Tilman says when someone eats a meal they are responsible for the little share of fertilizer a farmer somewhere had to apply to grow a crop. If the meal is from farm-raised animals, like the heaping plates of meat served here, the amount of fertilizer is much greater than if it’s from plants.

“It takes from three to ten kilograms of grain to produce a single kilogram of meat.”

Tilman says if Americans ate less meat, they could dramatically reduce fertilizer usage. However, per capita consumption is rising. Meat consumption is on the rise globally as well. David Tilman would like that to change. He says if current trends continue, human production of nitrogen nutrients will grow to triple or quadruple what nature makes on all Earth’s lands. Professor Tilman says that in many places the impact on the environment would be catastrophic.

For the Great Lakes Radio Consortium, this is Daniel Grossman.

Algae: The Missing PCB Link?

Toxic chemicals known as P-C-B’s haven’t been used in the U.S. for morethan two decades. But dangerous levels of P-C-B’s remain in the naturalenvironment and pose a threat to human health. To address this problem,scientists are trying to understand how these chemicals get into thefood chain. Now, a scientist at Northwestern University has found alikely answer. The Great Lakes Radio Consortium’s Steve Frenkelreports: