Too much of a good thing: Consequences of overplanting Bt corn in the US

Michigan State University

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Why this matters:

• Too much of a specific type of Bt corn — genetically modified to produce insecticides against corn rootworm — is being planted in places that don’t have a high risk of corn rootworms destroying corn crops.

• This overuse is causing corn rootworms to become resistant, or immune, to Bt insecticides. So Bt corn isn’t working as well now in Corn Belt states where corn rootworm is a serious risk, as rootworms are becoming increasingly pesticide resistant.

• Corn rootworm is one of the worst pests for corn in the U.S. — it can cost over $1 billion in crop damage per year.

EAST LANSING, Mich. – A new study from Michigan State University shows that planting too much genetically modified corn designed to fight off a tough insect — the corn rootworm — especially in the eastern U.S. Corn Belt states may be causing more harm than good.

Bt corn was created to produce natural pesticides, through the introduction of genes from a soil bacterium called Bacillus thuringiensis, or Bt for short. Some varieties of Bt corn kill corn rootworms by making the roots poisonous to them, though the corn is safe for humans and animals. But after years of research across 10 states in the U.S. Corn Belt, scientists have found that the more this corn is planted, the less effective it becomes.

According to study author, Felicia Wu, a John A. Hannah Distinguished Professor at MSU, whose graduated doctoral student Ziwei Ye served as lead author of the study, the U.S. is the largest field corn producing nation in the world, supplying nearly 40% of global corn exports.

“Field corn in the U.S. is used for human food, animal feed and ethanol production. We eat field corn in our cornmeal, grits, corn chips, corn flakes and corn tortillas — not as corn on the cob,” Wu said. “But field corn is plagued by the corn rootworm, which is one of the toughest, most amazing pests that exists. I like to think of the corn rootworm as ‘Loki’ because it’s a trickster — it just keeps evolving resistance to everything we throw at it, not just pesticides or Bt corn, but even crop rotation. And it’s costing farmers billions of dollars.”

So, why has ‘Loki’ become increasingly resistant to the built-in protection of Bt corn? Wu and this research team found farmers were planting more Bt corn than they needed, especially in the eastern Corn Belt states — Ohio, Michigan, Pennsylvania — with no added benefit and higher seed costs. These eastern states don’t have nearly as much of a corn rootworm problem as the major corn producers in the West, which include Iowa, Illinois and Nebraska.

“The problem is that farmers in the east Corn Belt states are overplanting Bt corn even though rootworm is not a problem,” Wu said. “So, we’re putting a lot of the Bt corn with roots containing toxins for corn rootworms into the environment. What this means is that the rootworm is going to evolve resistance more quickly, since it is Loki.

“One of the things that we’ve known in agriculture in general, not just for genetically modified crops, is that the more of a particular pesticide or antibiotic you put in the environment, the more quickly the pests or the bacteria evolve resistance to it because of selection pressure — it’s a matter of survival of the fittest. The organisms will find a way to survive.”

It’s already costing farmers more money because these Bt seeds containing proteins to target corn rootworm are more expensive — and unnecessary in the East. Every time a new trait is introduced to protect a crop, it adds an additional cost per seed. The study estimates that reducing the Bt planting rate from 50% to 18% in eastern states could have saved farmers $99 million in one-year benefits and $1.98 billion in lifetime benefits. ​

The study calls for more thoughtful and balanced use of Bt corn, including more seed options, including those that don’t protect for corn rootworm, and better communication with farmers. Wu said that to keep this powerful biotech crop working, we need to avoid overusing it and find a new approach that supports both farmers and the environment.

“We need to be more careful about the way we grow Bt corn,” Wu said. “There are less expensive corn varieties that farmers in the East can use that don’t protect against rootworm but do protect against other pests that they have. If we keep using corn rootworm-protected Bt varieties in the East, all we’re doing is shortening the amount of time before the entire industry is negatively impacted.”

The study was published in the journal Science. It was funded in part by the U.S. Department of Agriculture Natural Resources Conservation Service.

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Journal

Science

DOI

10.1126/science.adm7634 

What The Corn Industry Doesn't Want You To Know


Gina Badalaty
Sun, September 24, 2023 

hand holding ear of corn - Infusorian/Shutterstock

Corn is everywhere in the American household. This ubiquitous crop is on our plates, in our products, and even in our gas tanks. Maybe it's because of its versatility -- it can be considered a vegetable or grain, depending on when you harvest it. Because it has been modified to resist all kinds of external threats, a bumper crop is ensured every time so you can have perfect corn on the cob every summer.

Yes, corn is a modern wonder of technology found everywhere thanks to Big Agriculture (Big AG) -- those corporate entities that make millions from pushing factory-farmed corn across the country.

But this abundant crop has a dark side. Industrial farming with advanced technology has done far more harm than good to the planet, farmers, cattle, and workers. There are even questions about the health impacts and safety of Big AG corn.

The way America farms corn puts the entire industry and our food supply at risk. There are many things that the corn industry does not want you to know.

Read more: Mistakes You're Making With Your Corn On The Cob

Corn Farming Methods Increase Air Pollution

tractor and corn crops - Fotokostic/Shutterstock

Right off the bat, corn farming was recently found to be one of the top causes of air pollution. Studies show that 16% of all pollution caused by humans can be attributed to industrial farming processes including fertilization, seeding, and harvesting. These processes cause small, toxic particles to enter the atmosphere that we can actually inhale.

Recently, some researchers wanted to explore this problem in more depth. In the first study of its kind, the journal Nature Sustainability published a 2019 report that broke down each process involved with industrial corn farming and how they contribute to air pollution. They looked at the entire pre-harvest process around the U.S., from farming to fertilizer manufacturers. By combining corn production and emission models with what is known about how pollution impacts human health, they discovered that corn farming could be responsible for a stunning 4,300 premature human deaths per year.

GMO Corn May Be Bad For You

inspector looking at corn crop - Casarsaguru/Getty Images

Most corn in the U.S. today is produced by Big AG. These companies use genetically modified organisms (GMOs) to create herbicide-resistant corn. Bt corn is a GMO that carries a pesticide to ward off pests. The health hazards of this product are hotly debated. GMO foods have been accused of being an allergy trigger even though research shows that they are no more likely to cause an allergic reaction than their non-GMO counterparts.

Another accusation links GMOs to cancer and other health conditions. While the American Cancer Society has said there is no evidence linking the GMO pesticide, glyphosate, to cancer, the International Agency for Research on Cancer, part of the World Health Organization (WHO), called GMOs a potential carcinogen in 2015. The WHO dismissed the study, calling it tainted, but the agency disagrees. That said, many other studies are calling the safety of glyphosate into question. For example, new research has linked it to non-Hodgkin lymphoma.

Another challenge of GMO crops is that it allows for the rise of super pests. In Canada, the corn borer -- a moth that can devastate crops -- adapted to resist genetic modifications. Over time, according to some researchers, a similar resistance could become widespread among moth populations. If crops are at risk from pesticide-resistant pests, stronger -- and potentially more harmful -- solutions may be developed to protect corn.

Industrial Corn Farming Creates Toxic Algae

toxic algae in water - mivod/Shutterstock

Most of us understand that our oceans are polluted by many byproducts of modern convenience. Corn is no exception. Across America, our watershed resources are falling victim to toxic algae. This issue is primarily caused by industrial corn farming. These algae blooms come from the runoff of the phosphorus and nitrogen found in corn fertilizer. Algae outbreaks force authorities to shut off water supplies, which can cause water shortages.

Ironically, these fertilizers were promoted as an eco-friendly way to farm. The U.S. Farm Bill has authorized programs in the past that encouraged fertilizer runoff. Although they are not harmful themselves, they create a toxic form of algae in the water. Even the Environmental Protection Agency recognizes "nutrient pollution" as one of the country's worst problems contributing to climate change.

The issue is so prevalent that NASA recently designated satellite tools to track these algae blooms, which can clearly be seen from space. They estimate that nearly 2,000 tons of marine life have been killed due to these blooms, including fish, sea turtles, and marine mammals. And that damage is not just limited to wildlife. When algae come ashore at beaches, harmful toxins are released into the air that can cause respiratory problems in humans.

Corn-Based Ethanol Could Be Even Worse For The Environment Than Gasoline

ethanol factory blowing pollution - Simplycreativephotography/Getty Images

A recent study shows that ethanol, derived from corn, contributes far more to global warming [Note: That's a fairly well disguised misinformation site, hence the slide exclusion.] than regular gasoline. The research was published in February of 2022 and was partly funded by the National Wildlife Federation and the U.S. Department of Energy. The study concluded that ethanol releases far more carbon into the atmosphere than gasoline derived from petroleum. The main culprit here? Once again, industrial farming deserves the credit.

This study examined the U.S. renewable fuel standard, which has regulated fuel standards since 2005. The regulation requires all fuel produced in the U.S. has renewable fuel mixed into it. In other words, all standard gasoline available today has ethanol mixed in. Since then, the corn industry has grown and greatly profited from this regulation.

The Renewable Fuels Association accuses the study of faulty methods and incorrect assumptions. In 2019, the U.S. Department of Agriculture performed its own study, which claimed that the carbon emission of ethanol was far below gasoline. The debate continues, but with climate change at the forefront of politics, the corn industry needs to answer for its process.

Corn Crops Are One Of The Most Wasteful

man irrigating corn crops - Simonskafar/Getty Images

Factory-farmed corn is an incredibly wasteful crop. First, it requires a large amount of water to thrive. Because the corn industry is so immense -- comprising about a third of all industrial farming in America -- that the need for water during dry seasons and periods of drought is high. Irrigation must be employed, but as of 2017, corn uses more irrigation water than any other crop in the U.S. with some 12 million acres of irrigated farmland. Some systems are inefficient, too. The increased need for irrigation also leads to more fertilizer runoff and nutrient pollution.

Plus, much of the harvested crop ends up as waste. Only about a third of America's corn harvest is used for food today; the rest is split equally between ethanol and livestock feed. Nearly 50% of harvested plants are tossed aside and burned by many corn producers, including stalks, leaves, husks, and cobs. Researchers are now seeking ways to repurpose this corn waste into activated carbon rather than add more injury to the environment with these fires.

Corn Is Harmful To Ecosystems Around The Globe

man inspecting corn crop - Casarsaguru/Getty Images

From the U.S. to Brazil to the Amazon rainforest, the demand for corn has led to a loss of natural ecosystems. Factory-grown corn relies on monocropping, which destroys the beneficial biodiversity found in nature.

In traditional farming, land and crops are rotated. This is key to keeping the soil healthy, ensuring a plentiful harvest every season. Industrial farming, on the other hand, employs monocropping -- the process of exhausting the land by planting the same thing over and over. How did it become so popular?

Decades ago, global leaders wanted to create solutions to combat hunger. They believed that monoculture was the best way to increase crop yields. By creating large industrial farms dedicated to a single crop, they saved time and money.

However, with monocropping, when a crop fails -- as it might during a drought or when pests successfully work their way through the field -- it fails spectacularly.

But it gets worse. Countries around the world are destroying their native ecosystems to plant this monocrop. For example, Brazil's increase in corn production has increased deforestation of the Amazon Rainforest. And in Africa, water resources in areas at risk of drought are being depleted by corn irrigation. Such widespread loss of natural biodiversity and resources leaves us at serious risk of a global environmental disaster.

Industrial Corn Farming Creates New Risks

corn borer on corn cob - Bigc Studio/Shutterstock

Industrial corn farming also can breed new diseases. Scientists are already warning that a new pandemic danger could arise that impacts high yield crops instead of people. Once again, monocropping is at the root of the issue. When so many acres of farmland are dedicated to a single crop, the risk of a virus or bacteria wiping out much of the yield is comparatively high.

It's happened before. In the 1970s, a fungus swept through the U.S. Corn Belt, devastating 15% of the anticipated harvest. And today? Recently, a new bacterial disease spread through corn fields in one of those corn belt states: Texas. This fungus cost some farms up to 90% of their crops. The pathogen first struck in 2021 during a fungicide trial and in 2021 at seven farms. The corn industry could look for ways to re-introduce biodiversity to farming methods to protect both crops and the affected ecosystems.

Corn Crops Cause Soil Degradation

field soil degradation - Meryll/Shutterstock

There is yet another ecological challenge of industrial corn farming: Soil degradation. In 2021, satellite imaging demonstrated that the American Corn Belt has lost at least a third of its topsoil, with some farms losing as much as 50%.

That poorer soil quality means worse yields of corn, which could be quite a blow since this region produces 75% of corn in the U.S. And soil degradation is costing farmers millions of dollars in fertilizer to compensate for increasingly infertile soil. In other words, more and more nitrogen- and phosphorus-rich fertilizer is required, which contributes to greenhouse gas emissions and toxic algae in a vicious eco-cycle.

The farming industry must seriously consider rethinking its processes to maintain crop yield while protecting the environment; the current paradigm does not appear remotely sustainable. Better tools such as regenerative agriculture can help restore soil integrity and reduce costs, but will the corn industry listen?

Corn Feed Harms Cattle

Doctor looking over cattle - Tomazl/Getty Images

As mentioned, one-third of all factory-farmed corn is used for livestock feed. Unfortunately, this feed can lead to pain, illness, and death for livestock. Cattle are natural grazers. Their bodies are designed to ingest and process grass and other fiber-based foods. This helps maintain the microorganisms in their stomach system and aids in digestion, keeping the animals healthy.

Unfortunately, cattle grazing is more expensive for farmers than feeding them grain. Since corn is overproduced, it's cheaply available as feed. Feeding cattle grain is also more convenient for monocropping than grazing. It makes cattle gain weight faster, which is good for the beef industry.

Despite these benefits, eating grain is harmful to cattle. These animals have a unique stomach system adapted to eating grass, not grains. Eating grains causes gas buildup, making them bloat. This leads to inflammation that stresses their lungs, which can get so bad that cattle may slowly die of asphyxiation.

Besides this agonizing death, corn feed can cause other health issues in cattle, including abscess, tumors, and acidosis, which are prevalent among factory-farmed cattle.

Industrial Corn Farming Is Killing Small Farms

father and son on farm - Maksim Shmeljov/Shutterstock

Small- and medium-sized family farms are being gradually pushed toward extinction. The numbers prove it. In a 12-month period, farm bankruptcies increased 50% in the Northeast and 12% in the Midwest, in 2019. While several factors contribute to this phenomenon, the rise of factory farming, especially from products like corn, is the prominent cause.

How did this happen? In the '70s, the government pushed smaller farms to massively increase production. Many complied, but in 10 years, overproduction led to skyrocketing costs. This put many farms upside-down in debt. Some went bankrupt, leading corporations to sweep in to pick up the slack. These corporate farms make CAFOs -- short for "concentrated animal feeding operations." Today, CAFOs are the only way to run a farm and still earn a profit. Most small farms were forced to change from traditional farming, including dairy or livestock, to corn and soybean farming to stay alive. The crop is then sold as cattle feed for Big AG companies.

Some farmers claim that companies game the system by intentionally keeping prices low, hiring cheap labor, and preventing the remaining farmers from earning more. This caused many Midwestern farming towns to die out or slide into poverty as the CAFO companies turned a big profit.

Most Corn Is Grown On Farm Subsidies

female farmer with tablet - Simonskafar/Getty Images

Once the continual overproduction of corn became a reality, farmers needed subsidies supported by American taxes. This is another hotly debated issue, but many small farmers believe they have done more harm than good.

One point of contention is the problem of who truly benefits from farm subsidies. They should benefit farmers, but if they did, why would so many farms go bankrupt? However, there is conflicting information on this topic. The Cato Institute states that corn, soybeans, and wheat farmers get 70% of subsidies. Yet in 2018, Forbes found that the top 10 subsidy recipients earned over $150 million from their farms. Most commonly, subsidies go to the landowners. However, most working farmers today rent and, thus, do not receive any subsidies.

Subsidies encourage and support the proliferation of factory farming, which can harm the environment, cattle, towns, and people. And since they are regulated under the U.S. Farm Bill, which is reviewed by Congress every few years, this regulation can come with political strings attached, further muddying the integrity of the corn industry.

Corn Farms Exploit Laborers

worker with corn plant - encierro/Shutterstock

Most people know that many farm workers come to America from Mexico and other Central and South American countries to find jobs. You might not know how these workers are treated at industrial corn farms. They are hired by factory farms and paid very little, often less than the low wages they are promised.

As if that wasn't bad enough, some workers are actually trafficked. Workers are lied to about where they will work and then relocated to other farms. Housing conditions can be deplorable, with issues ranging from lice and roach infestations to broken water and bathroom facilities. But that's nothing compared to how they are treated.

One worker speaking to The Guardian revealed the details of a farm trafficking ring in Georgia. He was forced to work 12-hour days for 15 days straight for a total of $225. After that, he was moved to another farm to work for free and eventually returned to Mexico. Other migrants harmed by this ring claimed they were abused, tortured, or raped, and two workers died. Fortunately, this trafficking program was discovered and at least 24 defendants were indicted.

Unfortunately, investigation into this type of trafficking by the U.S. Department of Labor has significantly dropped over the years. This can lead to many more criminal trafficking organizations preying on migrant workers.

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Crop pests can develop ‘fighter-jet wings’ after eating specific mix of corn

North Carolina State University

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Corn earworm pests are aptly named as they feed on ears of corn.

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Credit: Photo courtesy of Steven Roberson, NC State University.

Eating a blend of non-toxic corn and genetically modified toxic corn can result in corn earworm pests (Helicoverpa zea) developing longer, more narrow and more tapered wings – shaped like the wings of a fighter jet – that can propel them long distances, increasing the chances the pests will spread resistance to the toxic corn. The findings add to knowledge about how crop diets can influence pest dispersal behavior.

The research suggests that a blend of corn that produces Bt toxin – designed to kill pests – and a small percentage of toxin-free corn can, in just one life-cycle generation, dramatically change the shape of moth wings to make them more aerodynamic, increasing the moth’s capability to fly longer distances.

“Wings from insects eating a blended toxic and non-toxic corn diet were stiffer and more able to travel in higher wind speeds,” said Dominic Reisig, professor and extension specialist of entomology at North Carolina State University and co-corresponding author of a paper describing the research. “These insects are able to get up into the winds and ride them longer distances.”

Researchers at NC State and colleagues wanted to learn if corn earworm pests growing up and eating toxic and non-toxic corn blend diets would have noticeable physical differences from pests that ate purely non-toxic corn or pests that ate purely Bt corn containing either two or three different toxins. The vast majority of corn and cotton grown in the United States contains Bt toxins to control insect pests.

Corn earworms are aptly named: they feed on corn ears. While corn yield loss is not greatly concerning, the pest also enjoys soybean, tomato and cotton plants, making it a ubiquitous pain for farmers. 

“Corn is basically like a factory for this insect,” Reisig said. “Corn earworm can overwinter in our state, slowly build up its generations early in the season, and then in July, when corn silks, those moths go in and lay eggs, Almost every single ear of corn produces at least one caterpillar that becomes a moth when it grows up. That’s a lot of bugs. All of that activity also funnels into cotton and soybeans, and that’s why they’re such a big problem.” 

The researchers compared wing shapes of moths raised on the blended corn; moths raised exclusively on non-Bt corn; moths raised exclusively on Bt corn containing two different toxins; and moths raised exclusively on Bt corn containing three different toxins.

The results showed that the wings of moths eating the three non-blended corn diets were less aerodynamic and more brittle and deformed, making those moths less apt to travel long distances.

Moreover, moths eating the blended diet showed wing shape changes after just one generation, a striking physical transformation.

“It appears that resistance occurs faster when worms eat these blends, creating individual moths that have multiple resistance mutations,” Reisig said. “This is one more piece of evidence that blending Bt and non-toxic corn pollen is really dangerous for resistance.”

Reisig adds that his program’s work continues on the effects of Bt corn and non-Bt corn diets, including on corn earworm mating success.

K M Mikac, M J Powley, S Barclay, J H Dominguez Davila and D Pezzini co-authored the paper, which appears in Environmental Entomology. 

The work received support from a Biotechnology Risk Assessment Grant, project award no. 2018-33522-28741, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. This research was also supported by a University Global Partnership Network (UGPN) grant (2022-23).

- kulikowski -

Note to editors: The abstract of the paper follows.

“Helicoverpa zea selected on Bt corn have wing shapes better suited to long distance flight”

Authors: K M Mikac, M J Powley, S Barclay, University of Wollongong; J H Dominguez Davila, South Coast Structural Engineers; D Pezzini and Dominic Reisig, NC State University

Published: Nov. 19, 2025 in Environmental Entomology

DOI: 10.1093/ee/nvaf117

Abstract: Evolution of resistance within insects to pest control has resulted in changes to the organism’s morphotype, including changes in wing shape. Both geometric morphometric and finite element method (FEM) were used to examine wing changes in Helicoverpa zea sampled from four different Bt corn treatments in North and South Carolina, USA. The four treatments were: pure-stand non-Bt corn (treatment 1), pure-stand Bt corn with two toxins (Cry1Ab and Cry1F; treatment 2); pure-stand Bt corn with three toxins (Cry1Ab, Cry1F, and Vip3A; treatment 3); and seed blended Bt corn with 80% containing three toxins (Cry1AB, Cry1F, and Vip3A) and 20% having no toxins (treatment 5). Geometric morphometric analyses revealed significant wing shape differences in both female and male moths were driven by moderately selected moths (treatments 2 and 5). Male and female moths, especially from treatment 5, had longer and more slender forewing shape conducive for longer distance flight. FEM modelling of the flight potential in both male and female H. zea, revealed that the highest wing elastic deformation values for wind speed, indicating the most impact on wing structure, occurred for treatment 2> treatment 1> treatment 3> treatment 5. Wing elastic deformation was significantly more pronounced in female than male moths. In conclusion, we found that one generation of selection on Bt corn in the field, could induce H. zea wing phenotypes more conducive for potential long-distance dispersal and should be further investigated by directly testing the impact on migratory flight. Our study contributes to the growing body of evidence that selection of H. zea on Bt crops may influence adult dispersal behavior.

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Journal

Environmental Entomology

DOI

10.1093/ee/nvaf117 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Helicoverpa zea selected on Bt corn have wing shapes better suited to long distance flight

Article Publication Date

29-Nov-2025

 

Corn after soy: New study quantifies rotation benefits and trade-offs

University of Illinois College of Agricultural, Consumer and Environmental Sciences

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Corn-soybean rotation is the most common cropping sequence in the U.S. Midwest, known for improving corn yield compared with continuous corn. New University of Illinois Urbana-Champaign research reveals the underlying mechanisms and impacts on crop productivity, environmental sustainability, and economic returns of these rotations. 

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Credit: Ziyi Li, University of Illinois Urbana-Champaign

URBANA, Ill. -- While the majority of Midwestern farmers rotate corn and soybeans, commodity prices and corn yield advantages compel some to plant corn year after year. Although foundational research on the benefits of corn-soybean rotation goes back decades, University of Illinois Urbana-Champaign scientists are working to address remaining holistic questions about crop yield, environmental impacts, and economic returns under various crop rotation scenarios. 

In a new study, researchers from the university’s Agroecosystem Sustainability Center and the College of Agricultural, Consumer and Environmental Sciences used the sophisticated agroecosystem model ecosys to explain why corn yield is higher after soybean at normal nitrogen fertilization rates; how corn-soy rotation impacts soil greenhouse gas emissions and nitrogen leaching; and when corn-soy rotation is most economically advantageous.

“We found that while corn-soy rotation can boost corn yields and reduce nitrogen fertilizer needs, the benefits come with nuanced environmental and soil carbon trade-offs,” said study leader Kaiyu Guan, founding director of the ASC and ACES Levenick Professor in the Department of Natural Resources and Environmental Sciences at Illinois.

Fertilizer rates determine corn yield boost from rotation

After training the ecosys model on a decade’s worth of Department of Crop Sciences field trials with varying rotations and nitrogen fertilizer rates, the researchers were not surprised to find corn grown after soybeans consistently yielded about 6.4% more, on average, than continuous corn, at standard nitrogen rates (151 kilograms of nitrogen per hectare). 

Diving deeper, the team found that the lower biomass and faster breakdown of soybean residue left the soil surface more exposed in spring, when corn is planted. Exposed soils warm more rapidly, which in turn causes soil microbes to mineralize more nitrogen from organic matter, providing a source of available nitrogen for young corn plants — an effect much like starter fertilizer commonly used by farmers. The researchers found this led to greater corn yield by the end of the season. 

However, this advantage decreased with higher nitrogen fertilizer rates. 

“The more nitrogen you add, the less yield benefit you get from rotation,” said the study's first author Ziyi Li, research scientist at ASC. “In some cases, the yield boost nearly disappears.”

Rotation reduces emissions, but affects soil carbon and nitrogen loss

From an environmental standpoint, corn-soy rotation helped reduce nitrous oxide and ammonia emissions from soils. But the fast-decomposing soybean residues led to an overall reduction in soil organic carbon compared to continuous corn.

Not surprisingly, nitrogen leaching was lower in soybean years due to the absence of fertilizer application. However, the fact that there was still nitrogen leaching under soybeans points to the importance of nitrogen mineralization from organic matter. Leaching increased in subsequent corn years when decomposed soybean residues released nitrogen into the soil. 

“These results underscore a key trade-off,” Guan said. “Rotation improves some sustainability metrics while compromising others, especially under typical fertilization practices.”

Economic returns favor rotation, but depend on fertilizer use and market prices 

Using historical commodity prices, the researchers found that corn-soy rotation offered higher economic returns — up to $458/acre ($1,133/hectare) more than continuous corn — at low nitrogen fertilizer rates (45 pounds/acre) and under typical market conditions (soybean: $11/bushel, corn: $4.50/bushel, and N fertilizer: $193/Mg ($175/short ton) UAN). But under high nitrogen inputs and market scenarios with elevated corn prices, this advantage was significantly reduced or even reversed.

“The extent to which one cropping system outperforms the other in terms of net agronomic benefits depends on more than just corn yield and nitrogen fertilizer usage, but also needs to consider soybean yield and market-driven prices, including fertilizer, grain, and costs such as machinery,” Li said. “Such comprehensive economic assessments can help farmers make informed decisions about crop sequences, especially in response to market fluctuations, and inform insurance products and conservation initiatives accordingly.”

No universal approach

The study underscores the importance of tailoring nitrogen management to balance profitability and sustainability. Lower fertilizer rates in corn-soy rotation compared with continuous corn can maximize economic return while mitigating some environmental impacts, but farmers must weigh these benefits against potential declines in soil organic matter and greater nutrient leaching. 

“Our work gives farmers and policymakers a more holistic view of organic matter, nitrogen, and yield outcomes,” said co-author Andrew Margenot, associate professor in crop sciences at Illinois. “We’ve known that these components matter and how they respond individually, but tying them together to show the interconnectedness is key.” 

Additionally, Margenot points out that this work underscores the need to consider long-term changes in organic matter given its importance as a source of nitrogen for crop uptake. 

“These results are consistent with increased nitrogen mineralization under soybean than corn, and declines in organic matter being driven by soybean in the corn-soybean rotation,” he said. 

Decades of research have pointed to advantages of crop rotation in terms of yields, reduced fertilizer needs, and soil health. The new study provides a robust scientific rationale for rotation and fills a previous knowledge gap by quantifying the agricultural outcomes of corn-soy rotation in detail. Despite the environmental tradeoffs discovered by the team, the economic analysis demonstrates that crop rotation is profitable, especially at lower fertilizer rates.  

The paper, “Comparing continuous-corn and soybean-corn rotation cropping systems in the U.S. central Midwest: Trade-offs among crop yield, nutrient losses, and change in soil organic carbon,” is published in Agriculture, Ecosystems and Environment [DOI: 10.1016/j.agee.2025.109739]. The research was supported by the Illinois Nutrient Research & Education Council, Illinois Soybean Association, the National Science Foundation, the NASA Acres Program, the U.S. Department of Energy’s ARPA-E SMART-FARM program, and the USDA National Institute of Food and Agriculture.

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Journal

Agriculture Ecosystems & Environment

DOI

10.1016/j.agee.2025.109739