Farmers buy 88 million tons of nitrogen fertilizer annually to grow staple crops such as corn, wheat and rice. And it takes 3 to 5 percent of the world’s natural gas to make all that fertilizer. That’s frustrating because three-fourths of the Earth’s atmosphere is nitrogen, but it’s in a form that most crops can’t use.
But a few plants, such as alfalfa, soybeans and peanuts, can fertilize themselves, in a way, thanks to a friendly bacterial infection. These legumes recruit bacteria that “inhale” naturally occurring nitrogen from the atmosphere and convert it into the useful form that plants use for food.