"The 50 Greatest Breakthroughs Since the Wheel."

"The Atlantic recently assembled a panel of 12 scientists, entrepreneurs, engineers, historians of technology, and others to assess the innovations that have done the most to shape the nature of modern life."

I was interested to see nitrogen fixation at #11, because it's something I've got to tell you I had never thought much about that at all until last week when I was reading this excellent New Yorker article by Elizabeth Kolbert, "Head Count, Fertilizer, fertility, and the clashes over population growth," which begins with this topic:

Early in the history of agriculture, people realized — without, obviously, understanding the chemistry behind this insight—that when usable nitrogen ran low fields turned barren. Eight thousand years ago, farmers in the Middle East were already planting legumes, whose roots harbor nitrogen-fixing bacteria, in rotation with cereal crops, such as wheat. Later, Cato the Elder recommended that Romans “save carefully goat, sheep, cattle, and all other dung.” Bird shit is an excellent source of nitrogen, and in the early nineteenth century, when Europeans learned that there were mountains of the stuff on remote islands off Peru, the discovery inspired a guano rush; by the eighteen-fifties, Britain was importing four hundred million pounds of bird poop a year, and the United States a hundred and seventy million pounds....

By [Fritz] Haber’s day, the appetite for crop-friendly nitrogen was so huge that scientists had turned their attention skyward. Nitrogen is the most common element in the earth’s atmosphere.... but almost all of it is floating around in the intractable form of N2. When... Haber showed how to bust up N2 to produce ammonia — NH3 — he basically solved the problem. No more guano would be needed. Haber had, it was said, figured out how to turn air into bread.