Keeping barnyard sludge under control

Cows munching grass instead of corn could cut nitrogen pollution

April 3, 2015
Food grown to feed cows might be suffocating fish. [Image credit: Flickr user lynn Dombrowski]

It takes more than a muck-rake and a wheelbarrow to keep a barnyard clean, especially when so much of modern agriculture relies on heavy use of synthetic chemicals and large numbers of animals packed into small spaces. The U.S. Environmental Protection Agency released an evaluation March 16 on how well New York state farmers are doing in keeping the nearby water supplies free of contaminants. The state is on track in some areas, but certain aspects such as nitrogen pollution and grazing need more attention, the report found.

There are more potential hazards involved in, say, dairy farming than you might initially think. And barnyard manure washing into streams and contaminating them with fecal matter is just the beginning. Chemicals potentially dangerous to the environment are used to wash milking equipment. When animals die, their decomposing corpses can harbor harmful bacteria that can get into the water supply. Finally, growing feed for the cows requires nitrogen, phosphorous and pesticides, all of which can wash into surrounding rivers and lakes and harm natural environments.

Each year, the EPA assesses the chemicals found in New York State’s water supply, and inspects farms across the state to monitor the efficacy of pollution-control policies. The agency also tracks yearly progress toward goals to cut nitrogen, phosphorous and sediment pollution in streams and rivers to minimal amounts by 2025. This year, the agency found phosphorous and sediment levels were on track to meet these goals, but that nitrogen usage has increased.

That’s concerning because when there is too much nitrogen in the water, algae populations explode. Algae gobble up the extra nitrogen and reproduce so fast that algae-eating animals can’t keep up. The algae grow so rapidly that they can eventually soak up all of the dissolved oxygen in the water, killing fish and creating an environment perfect for harmful bacteria. When farmers fertilize their fields with nitrogen to make a nutrient-rich environment for the crops, some of that nitrogen washes into the water and pollutes it.

One way farmers can mitigate this problem is by changing from feeding their animals crops like grain and corn to alternatives like prescribed grazing, according to the EPA report. In this grazing system, animals are shuffled between areas to graze instead of being fed corn or other feed crops. The animals get all their sustenance from the fields — no nitrogen heavy fertilizers required. By avoiding plowing (and the subsequent erosion that can follow) the land is more fertile and better for grazing. Even if the farmer occasionally uses a pasture for crops — to overwinter his animals for example — less nitrogen is used on this fertile ground so less polluted water runs off.

Unfortunately, not enough farmers and ranchers are using prescribed grazing. The EPA goal is to see the technique used on 90 percent of the 152,221 acres of available pasture by 2025. But they are less than halfway to their goal. The EPA report notes that most prescribed grazing programs are merely voluntary for farmers, but suggests that the time has come to consider making them mandatory, a step that the report authors say could lead to better control of manure and invasive species.

About the Author


Leave a Reply

Your email address will not be published. Required fields are marked *


The Scienceline Newsletter

Sign up for regular updates.