Photos by Chris Maggio

The Corn That Grows Itself

How microbes could upend America’s toxic dependence on nitrogen fertilizer

Andrew Zaleski
Published in
15 min readJun 13, 2019


CCrabs, clams, and worms die almost immediately. Fish, shrimp, and any animal that can swim quickly enough make valiant, though often doomed, efforts to flee. There are few places to go in a dead zone that can reach the size of New Jersey.

The Gulf of Mexico hypoxic zone — or “dead zone,” as it’s more commonly known — is a stretch of seawater where vast swaths of slimy algae bloom annually. When the algae eventually die, they decompose, sucking up so much of the water’s oxygen that all nearby aquatic life suffocates. In 2017, this dead zone measured 8,776 square miles, the largest since scientists at the National Oceanic and Atmospheric Administration began recording it in 1985. This summer’s dead zone is expected to be the second-largest on record at 8,717 square miles, according to scientists at Louisiana State University.

You can find the source of the dead zone by traveling north out of the Gulf, up the Mississippi River, and through its tributaries as they branch out into the agricultural nervous system of the U.S. In the rich, black soil of the Midwest, you’ll find the culprit: nitrogen fertilizer, the backbone of modern industrial farming.

Farmers around the world use 120 million tons of nitrogen fertilizer each year. (Another 54 million tons is added in the form of things like manure and atmospheric deposition.) In the U.S., much of the fertilizer goes into the Corn Belt — an area stretching from Nebraska to Ohio, Minnesota to Missouri. There, 6 million tons of nitrogen fertilizer are spread across farmland every year.

Close to 100 million tons of nitrogen added to the world’s crop fields are lost to the environment every year, either as gas emissions or as runoff.

While nitrogen fertilizer deserves considerable credit for driving a century-long global increase in crop yields, it’s also nasty stuff. The chemical factories that produce the material expel as much greenhouse gas into the atmosphere as all of the houses in America combined. Fertilizer is finicky and its application is often wasteful. Because it’s easily washed…