Nitrogen independence crucial to sustainability

Nitrogen is the fertilizer nutrient used in the greatest quantity in our country, with 12.5 million tons consumed in 2008. In the past decade, the amount we import from abroad has dramatically increased from only 12 percent in 1999 to 52 percent in 2008.

Production of nitrogen fertilizer with the Haber-Bosch process uses natural gas as a feedstock and requires a large amount of energy, so the production has shifted to countries where natural gas is abundant, such as Trinidad and Tobago, Canada and Russia. Because nitrogen fertilizer manufacturing is so closely linked to the hydrocarbon economy, many of the issues related to the sustainability of our energy supply — such as greenhouse gas emissions, limited reserves and increasing costs — affect the sustainability of our nitrogen fertilizer supply, too.

Luckily, nature has already provided us with a simple biological solution to the nitrogen problem. Our atmosphere is made up of 78 percent nitrogen gas, and bacteria that live symbiotically in the roots of legume plants are able to convert atmospheric nitrogen into a form that plants can utilize. This process is fueled with energy created by plants from sunlight, water and air instead of the fossil fuels used to manufacture synthetic nitrogen fertilizer.

Farmers can use legumes as cover crops, sometimes called “green manures,” to accumulate nitrogen from the atmosphere in plant tissue. When the cover crops are killed, the tissues decompose and release the nitrogen into the soil for the next crop to utilize.

Organic farmers routinely use legume cover crops as a source of nitrogen fertility for their crops. Research by the U.S. Department of Agriculture in Beltsville, Md., indicated that an organic grain crop rotation required half the energy input of the nonorganic crop rotations tested, largely because the organic rotation replaced nitrogen fertilizer with legume cover crops and manure.

At Penn State, research

into organic systems led by Mary Barbercheck, Jason Kaye, Dave Mortensen and Bill Curran has revealed how a legume cover crop can be managed to provide nitrogen fertility and suppress weeds and support beneficial insects, reducing the need not just for fertilizer, but for herbicides and insecticides, too.

Increasing numbers of nonorganic farmers in our county and state also are starting to use legume cover crops to reduce nitrogen fertilizer use.

At a field day in September organized by Joel Myers, a farmer in Spring Mills, and Craig Altemose, Penn State Cooperative Extension educator in Centre County, more than 40 people met to see how different types of winter cover crops, many of them legumes, affected this year’s corn crop. While results from the experiment aren’t conclusive, it was clear that many farmers in the area are actively seeking ways to use cover crops to reduce nitrogen fertilizer inputs.

There are many more questions still to be addressed as we collectively work to reduce our nitrogen fertilizer consumption in the region. But the partnerships among farmers, university scientists, cooperative extension educators and community organizations have already made inroads to nitrogen fertilizer independence.

Read more: http://www.centredaily.com/2010/10/29/2303408/nitrogen-independence-crucial.html#ixzz13kOZnfto