The atmosphere is about twenty-percent oxygen and eighty percent nitrogen from Earth's surface to where space begins at one-hundred-twenty kilometers up.

VOA: special.2011.04.06

University of Virginia professor Jim Galloway calls synthetic nitrogen fertilizer a "wonderful invention" because it increased food production.

VOA: special.2011.04.05

But he says many parts of the world use too much nitrogen fertilizer, and that harms the environment.

VOA: special.2011.04.05

Scientists at the agroforestry center say the use of fertilizer trees can reduce the need for chemical nitrogen by up to three-fourths.

VOA: special.2009.09.01

But the Chinese farmers used six times more nitrogen, and produced almost twenty-three times more surplus nitrogen.

VOA: special.2009.07.28

"For large animals like beef, a very large fraction of the nitrogen that enters the cow's mouth is excreted out the back end."

VOA: special.2011.04.05

The list is quite long." So Professor Galloway and other researchers have developed a nitrogen footprint calculator.

VOA: special.2011.04.05

There was a new system of liquid nitrogen to keep the pilot cool and to resist the crushing force of gravity at high speeds.

VOA: special.2010.07.07

The nitrogen calculator is currently designed for people in the United States, Germany and the Netherlands.

VOA: special.2011.04.05

Nitrogen runoffs from farms can create large dead zones, like those in the Gulf of Mexico.

VOA: special.2009.07.28

Other plants take nitrogen out of the soil, but beans and other legumes replace it.

VOA: special.2009.03.24

They take nitrogen out of the air and put it in the soil.

VOA: special.2009.09.01

Some experts say the best fertilizers for beets are low in nitrogen.

VOA: special.2010.03.02

And as it breaks down, it naturally releases nitrogen into the soil.

VOA: special.2010.06.01