The Omnivore's Dilemma: A Natural History of Four Meals

by Michael Pollan

All life depends on nitrogen; it is the building block from which nature assembles amino acids, proteins, and nucleic acids; the genetic information that orders and perpetuates life is written in nitrogen ink. (This is why scientists speak of nitrogen as supplying life’s quality, while carbon provides the quantity.) But the supply of usable nitrogen on earth is limited. Although earth’s atmosphere is about 80 percent nitrogen, all those atoms are tightly paired, nonreactive, and therefore useless; the nineteenth-century chemist Justus von Liebig spoke of atmospheric nitrogen’s “indifference to all other substances.” To be of any value to plants and animals, these self-involved nitrogen atoms must be split and then joined to atoms of hydrogen. Chemists call this process of taking atoms from the atmosphere and combining them into molecules useful to living things “fixing” that element. Until a German Jewish chemist named Fritz Haber figured out how to turn this trick in 1909, all the usable nitrogen on earth had at one time been fixed by soil bacteria living on the roots of leguminous plants (such as peas or alfalfa or locust trees) or, less commonly, by the shock of electrical lightning, which can break nitrogen bonds in the air, releasing a light rain of fertility.