Rotation Boosts Corn Yields with Fertilizer Balance

Jun 24, 2025
By Farms.com

Research Links Crop Rotation to Yield Gains and Lower Emissions

University of Illinois researchers have quantified the effects of corn-soybean rotation on yields, soil health, and profits using advanced modeling and a decade of field data.

The study confirms that rotating corn after soybeans increases yield and reduces the need for nitrogen fertilizer.

The average yield gain for corn after soy was 6.4% at standard nitrogen levels. Researchers found soybean residue breaks down quickly, warming the soil and promoting nitrogen mineralization — aiding early corn growth.

Ziyi Li, the study’s lead author, said, “The more nitrogen you add, the less yield benefit you get from rotation. In some cases, the yield boost nearly disappears.”

The rotation helps reduce greenhouse gas emissions but reduces soil organic carbon due to fast soybean residue decay. While nitrogen leaching was lower during soybean years, it increased during corn years due to nitrogen release from soybean residue.

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

Economically, the rotation proved more profitable, offering up to $458 per acre more than continuous corn when nitrogen use was low and market conditions were typical. However, profitability shifts under high corn prices and high nitrogen rates.

The study encourages farmers to manage nitrogen use wisely and consider soil health impacts. “Our work gives farmers and policymakers a more holistic view of organic matter, nitrogen, and yield outcomes,” said co-author Andrew Margenot.

Funded by USDA, NASA, and other partners, the research bridges the gap between science and real-world farm decisions, offering tools to balance sustainability and productivity in modern agriculture.

Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”