Table of Contents

How Does Corn Farming Work and Is It Bad for the Environment?

March 1, 2022

If the United States had a vanity license plate, it could easily be, “CORN FED.” Corn is in pretty much every aisle of your nearest grocery store. It’s also in our hair, where traces of what we eat can be found with laboratory testing. 

Yet the story of corn reaches into antiquity. Corn is a sacred, cultivated plant developed thousands of years ago by Native American communities. In this tradition, corn is called maize and is not just an object to be bought and sold, but a spiritual teacher. As described by food systems activist and farmer Leah Penniman, this gift of the First Peoples of the West to the rest of the world has since been appropriated, exploited, and commodified by white colonizers.

What Is a Corn Farmer?

The spread of corn into so many of our products is one subject of the 2007 documentary, “King Corn,” about how two descendants of Iowa farmers took over one acre of farmland to grow corn with modern farming techniques. A corn farmer is someone who owns or rents land on which they grow corn, usually to make a living. From the perspective of “King Corn” narrators Ian Cheney and Curt Ellis, corn is a raw material. It’s used to make food for humans and nonhuman animals. Examples of corn products include corn starch, corn gluten meal, hydrolyzed corn protein, and high-fructose corn syrup that has been increasingly added to processed foods. Corn that is fed to cows, chickens, pigs, and other farmed animals in concentrated animal feeding operations (CAFOs) also ultimately becomes human food in the form of beef, chicken, pork, and other meats. 

The kind of corn Cheney and Ellis grew, however, is not the kind of sweet corn on the cob we eat for dinner. The Nebraska Corn Board reports that 99 percent of corn grown in Nebraska is “field corn” and only 1 percent of corn is made for eating, starches, and decoration. Field corn is also called “dent corn,” and it’s what we use to feed animals and for other industrial uses like making ethanol.

The  sector that uses the most corn grown in the U.S. is animal agriculture, which uses corn and residual corn from ethanol production to feed to farmed animals. . Roughly another third of the corn is used to make ethanol. Corn in the form of high-fructose corn syrup is also used as a cheap replacement for sugar, fuelled by subsidized corn production. So it’s a catalyst for fast food: soda, french fries, and burgers. Other uses of corn include turning it into starch, vegetable oil, and alcohol.

Where Does Corn Grow in the U.S.?

Although corn grows throughout the United States, America’s corn belt is in the midwestern states: Iowa, Illinois, Indiana, and parts of South Dakota, Nebraska, Kentucky, Ohio, and Missouri. About one-third of the roughly 92 million acres of corn grown in the U.S. each year is produced in Iowa and Illinois, according to the USDA. 

How Much Corn Does the U.S. Produce?

Corn is the largest crop grown in the U.S. and uses the most land. In 2021 U.S. farmers and farmworkers produced about 15.1 billion bushels of corn. The United States produced about 32 percent of the world’s corn in 2021—384 million metric tons.

How Does Corn Farming Work?

Corn is a grass plant, just like the grass that grows in urban parks and suburban lawns throughout the United States. ”It is a gigantic version of that grass,” says the agronomist Ricardo Salvador in “King Corn.”

Farm Subsidies

When Cheney and Ellis set out to start their one-acre corn farm, they were told they would receive a direct payment of about $28 from the federal government before they even started preparing the land. Without this, and other subsidies like it, they would have lost money on the project. It turns out that funding from the government is crucial to keeping the economy of their great-grandparents’ Iowa corn-farming town afloat.

These payments are the result of a decision by U.S. Secretary of Agriculture Earl Butz in the 1970s to stop limiting the production of corn. Before this the U.S. government had been paying farmers not to grow too much corn, as a way to stabilize prices. 

After the government decided to instead massively fund the production of corn and increase exports, the crop became a raw material to make affordable food. As seen in “King Corn,” Butz liked to point out that people used to spend twice as much on their food—up to 16 to 17 percent of their take-home pay. 

Another impact that Butz’s decision had on farms was encouraging them to get bigger and make use of the advantages of producing at scale, which then squeezed out smaller farms. In 2013 the USDA described a doubling of farm size over the previous 25 years, meaning about half of all cropland in the U.S. is on farms with less than 1,100 acres, and half on farms with more, while that midpoint was 589 acres in 1982.

Contract Labor and Custom Services

Many corn farms contract with custom service providers for particular field tasks like spraying and harvesting. Larger farms are also more likely to contract with labor providers, and to lease equipment and other capital. On a video on the United Farm Workers’ Facebook page from 2020, Joaquin is hunched over weeding cornfields in Oregon. Joaquin plucks weeds by hand as he waddles over a row of dirt to protect baby corn plants. The laborer wears long pants, a long shirt, gloves, a safety vest, and a hood. In another video from 2018, corn farmworkers in Indiana are wearing garbage bags to protect themselves from the morning dew and from getting cut. 

Farmworkers working for contracted labor providers often experience workplace violations and abuse, including within the corn farming industry. Seed-corn companies like Monsanto and Pioneer bring in “thousands of migrant workers to the fields each growing season,” relying on them to detassel corn to produce their proprietary seeds. Farmworkers in corn fields are also exposed to pesticides and chemicals that are harmful to human health at a higher rate than other U.S. workers, as testified to the Idaho State Senate in 2020 by Areli Arteaga, a farmworker advocate with the United Farm Workers.


On their experimental one-acre corn farm, the makers of “King Corn” drove a tractor over their land with a big tank of ammonia trailing behind them. They injected 150 pounds of anhydrous ammonia in the ground, which would allow them to grow four times as much corn as their great-grandparents did. The mass production of ammonia for agriculture only became cost-effective after it was pioneered by the government-funded weapons industry to produce explosives during World War II.

Planting GMO Corn

Most corn grown in the U.S. (92 percent) is genetically modified. In “King Corn,” it only took Cheney and Ellis 18 minutes to plant 31,000 kernels (corn seeds) of Liberty Link (a brand of corn seed) in their one acre of land. They used a machine that planted the seeds in 32 parallel rows, chopping through the soil with toothed metal wheels.

When Cheney and Ellis spoke with the journalist and author Michael Pollan, he explained that modern corn plants now live in “cities of corn.” Because corn can now be planted closer together than before industrialization, one acre can be expected to yield about 200 bushels of corn, or 5 tons of food. 


To fight weeds, Cheney and Ellis hooked a sprayer machine to their tractor with a wingspan of 90 feet. It released a fine mist of Liberty herbicide over each row from a giant comb structure. Weeds like hemp, lambs quarter, and cocklebur died while the Liberty herbicide allowed the Liberty Link corn to grow. A month later, in July, the one-acre farm in “King Corn” was full of tall, green stalks of corn towering to about 6 feet in height. 


Their dent corn would be left in the field to dry—looking forgotten, dead, and brown—before being  harvested using a huge, boxy, combine machine in November. At that point, the corn was taken to a communal grain building called the town elevator. There, it was weighed and gathered with corn from all the other farms in the area.

How Do Corn Farms Affect the Environment?

There are many environmental harms associated with modern forms of farming, and the same is true of modern corn farms—some of these are discussed below. 

Water and Ecosystems

Industrialized corn farms use a lot of water, which is draining groundwater in the middle of the U.S. The excessive fertilizer from corn farms also runs off into rivers and oceans causing dead zones that are harmful to marine life. There is now a dead zone in the Gulf of Mexico which threatens animals, plants, and whole ecosystems. Pesticides used on the farms are said to directly harm insects, honey bees, and birds. 


Two centuries of colonial, industrial agriculture in the United States has also led to soil erosion and degradation. Rather than growing corn in polycultures as Native Americans had done, U.S. farmers grew corn in monocultures and decimated their topsoil with similar environmental effects to clear-cutting a forest. Soil can store nearly three times the carbon of forests and other types of vegetation, but injecting it with fertilizers makes it hard for living beings to survive. This contributes to long-term damage to soil structure, which may make it hard to grow food in the future. 

Climate and Air

Applying fertilizer, using gas to run tractors, kicking up dust while tilling the land, and pesticide production are all major contributors to air pollution from corn farms. This air pollution from growing corn has been linked to 4,300 premature deaths a year in the U.S.—that is, a quarter of deaths due to agricultural air pollution. Applying ammonia was a key culprit for air pollution from corn farms. This pollution includes significant sources of greenhouse gas emissions, contributing to climate change.


Corn farms are part of an industry that is known for poor work conditions. Agricultural workers typically earn minimum wage, in jobs without health insurance, in environments that lead to respiratory ailments

Food Systems

As well as being a mainstay of intensive crop agriculture, the production of cheap corn is a component of industrial animal farming. It enables concentrated animal feeding operations (CAFOs) to confine and feed livestock for part or all of their lives in a way that harms animals and the environment


There is so much more to say about corn farms than we could review here. We hope that this summary provides  you with a better sense of how it has become the biggest crop produced in the United States, why it is everywhere in our foods, and what the effects are for animals, workers, consumers, and communities when it is grown on an industrial scale.