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Wed December 14, 2011
Putting Farmland On A Fertilizer Diet
The U.S. Department of Agriculture released a document yesterday that got no attention on the nightly news, or almost anywhere, really. Its title, I'm sure you'll agree, is a snooze: National Nutrient Management Standard.
Yet this document represents the agency's best attempt to solve one of the country's — and the world's — really huge environmental problems: The nitrogen and phosphorus that pollute waterways.
There's a simple reason why this problem is so big, and so hard to solve. Farmers have to feed their fields, before those fields can feed us. Without fertilizer, harvests would dwindle. But lakes, estuaries, and coastal waters lie downstream from highly fertilized farmland, and now they are choking to death on too much nutrition.
Those nutrients typically come from commercial fertilizer, but they don't have to. Organic growers need to feed their fields, too. Farmers can also use animal manure (which is really recycled fertilizer from the fields that fed those animals) and legumes — crops like alfalfa or chickpeas, which add nitrogen it to the soil.
The problem is, those nutrients don't stay where they're needed. They migrate into groundwater, streams, or the air, and everywhere, they cause problems. They feed the growth of microbes and algae, turning clear water cloudy and depriving fish and other creatures of essential oxygen. (There are other important sources of nutrient pollution as well, including urban sewage and the burning of fossil fuels, but fertilizer is the biggest.)
In the United States, the best-known casualties of nutrient pollution include the Chesapeake Bay and a portion of the Gulf of Mexico called the "dead zone." But similar problems exist in many other places as well, including lakes and coastal areas of China and Europe.
So around the world, environmentalists and scientists are mobilizing to fight the plague of over-nutrition. That's where the new USDA document comes in. It lays out a host of steps that farmers can take — and will have to take, if they get funding from certain USDA programs — to minimize the spread of nutrients outside farm fields.
Essentially, it involves putting farmland on a sensible diet. Only feed the land as much as it really needs. And don't apply fertilizer, including manure, when the crops don't need it. Also, try to capture and store any excess nutrients. For instance, grow wintertime "cover crops" that can trap free nitrogen before it leaches into groundwater.
Dave White, the head of USDA's Natural Resources Conservation Service, told reporters that the new guidelines "could have a tremendous, continental impact." The guidelines do not have the force of actual regulations, but state governments can make them mandatory. Maryland, which is fighting a desperate battle to clean up the Chesapeake Bay, already requires its farmers to come up with detailed "nutrient management plans" that are supposed to minimize, and hopefully prevent, nutrient runoff.
At yesterday's briefing, White suggested that farmers will follow these guidelines voluntarily, simply out of economic self-interest. Fertilizer is expensive, and wasting it costs money. "If you're looking for someone who wants to regulate agriculture, you're talking to the wrong guy," he said.
Yet a long-running experiment at Michigan State University's Kellogg Biological Research Station suggests that economic self-interest alone can actually work against a solution. The experiment, which has been studying the environmental impact of different farming practices for the past 20 years, shows that it is possible to dramatically reduce nutrient releases from farmland — but it seems to require farmers to scale back their expectations modestly, rather than pursuing the highest yields of the most profitable crop, which is corn.
Ken Staver, a research scientist for the University of Maryland, says getting the flood of nutrients truly under control will take many years. "It's incrementalism," he says. "We went in a wrong direction incrementally, and we're working our way back incrementally. It's not going to give us the water quality that we would wish for. But it's all moving in the right direction."