[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/03/EW-04-24-12-Lightning.mp3|titles=EW 04-24-12 Lightning]
Nitrogen is one of the key nutrients that plants need to grow. It’s bountiful in our atmosphere, comprising seventy-eight percent of the air we breathe. But atmospheric nitrogen needs to be converted to ammonia in order to be useful to plants.
This conversion, called nitrogen fixation, is performed naturally by certain micro-organisms, most notably those that live in the roots of legumes. That’s why these plants are so important in crop rotation.
In the early twentieth century, scientists developed the Haber-Bosch method to synthesize ammonia from nitrogen for industrial use in weapons and in fertilizer.
But one of the most unusual forms of nitrogen fixation occurs during lightning storms.
Jim Galloway is a professor of Environmental Sciences at the University of Virginia…
“When a lightning strike occurs, the molecule N2 reacts with the molecule O2, or atmospheric oxygen, and forms two molecules of nitric oxide – NO. That material has a relatively short lifetime in the atmosphere, and is either removed from the atmosphere by precipitation, or by the process we call dry deposition, which is how things are transferred from the atmosphere to the earth’s surface when it’s not raining, snowing, sleeting, or hailing.”
There, the nitrogen is available to nourish plants.
Even though lighting strikes throughout the world about four billion times per day, Galloway says it accounts for just a fraction of the natural nitrogen fixation.
“A trivial source – five percent or perhaps even less than five percent relative to other nitrogen sources in the atmosphere, and relative to biological nitrogen fixation in the soil.”
Still, the role of lightning in nitrogen fixation is a fascinating part of the natural cycle of this element on earth.
Web Extra
Full interview with Jim Galloway, professor of Environmental Sciences at the University of Virginia…
[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/03/Galloway_interview_edited.mp3|titles=Galloway_interview_edited]Photo, taken on October 5, 2006, courtesy of Paolo via Flickr.