With rising input costs and growing attention on sustainability, many Illinois farmers are revisiting a key management decision: crop rotation strategy. A checkoff-funded study led by Dr. Kaiyu Guan at the University of Illinois offers fresh information into how soybean-corn (S-C) rotations compare to continuous corn (C-C) systems—not just in yield, but in long-term environmental and economic impact. 

Using advanced agroecosystem modeling and over two decades of field data, the project evaluated how these two systems affect soil health, nitrogen use, greenhouse gas emissions, and profitability. 

Key Takeaways for Illinois Farmers: 

• S-C Rotations Boost Corn Yield: The data showed that soybean-corn rotations enhance corn yields in corn years, thanks to improved soil nitrogen availability and warmer early-season soil temperatures. 

• Environmental Wins with Soybeans: S-C systems significantly reduced nitrogen leaching and greenhouse gas emissions like nitrous oxide (N₂O) and ammonia (NH₃), making them a more sustainable choice compared to continuous corn. 

• Long-Term Trade-Offs: While S-C rotations offered environmental advantages, they also slightly reduced long-term soil organic carbon (SOC) levels compared to C-C. However, the overall agronomic and sustainability benefits still favor S-C in many situations. 

• Economic Impacts Depend on the Market: The profitability of S-C rotations hinges on the price of soybeans relative to corn and the cost of nitrogen fertilizer. In years with high input prices or favorable soybean markets, S-C rotations may offer better economic returns. 

Farmers considering changes to their rotation system, especially those in high-input or environmentally sensitive areas, should look at soybean-corn rotations as a way to reduce nitrogen costs, lower emissions, and maintain strong corn yields. The model suggests that larger operations with a focus on long-term sustainability and input efficiency stand to benefit most. 

The Illinois Soybean Checkoff-funded study, powered by long-term data and real-world modeling, gives Illinois farmers another layer of information as they make rotation and nutrient management decisions heading into future seasons.  

For the latest project update, visit Field Advisor’s Research Hub.