All content for this article courtesy of the May issue of National Geographic. For full article and more photos, click here.
Credit: National Geographic
N. Nitrogen. Atomic number seven. Unnoticed, untasted, it nevertheless fills our stomachs. It is the engine of agriculture, the key to plenty in our crowded, hungry world.
Without this independent-minded element, disinclined to associate with other gases, the machinery of photosynthesis cannot function-no protein can form, and no plant can grow. Corn, wheat, and rice, the fast-growing crops on which humanity depends for survival, are among the most nitrogen hungry of all plants. They demand more, in fact, than nature alone can provide.
Enter modern chemistry. Giant factories capture inert nitrogen gas from the vast stores in our atmosphere and force it into a chemical union with the hydrogen in natural gas, creating the reactive compounds that plants crave. That nitrogen fertilizer-more than a hundred million tons applied worldwide every year-fuels bountiful harvests. Without it, human civilization in its current form could not exist. Our planet's soil simply could not grow enough food to provide all seven billion of us our accustomed diet. In fact, almost half of the nitrogen found in our bodies' muscle and organ tissue started out in a fertilizer factory.
Yet this modern miracle exacts a price.
Fertilizer runoff causes toxic algal blooms. This one covered a third of Lake Erie in 2011. © Peter Essick/National Geographic
Workers at a cooperative farm near Shanghai scatter fertilizer across fields of winter wheat. China is the largest producer and user of fertilizer in the world. Reluctant to limit fertilizer because of the country's history of famine, China overuses nitrogen by up to 60 percent. © Peter Essick/National Geographic
Chickens provide the fertilizer on this Pennsylvania farm. The mobile coops are relocated daily to distribute manure evenly so that it won't drain into the Chesapeake Bay. © Peter Essick/National Geographic