Cereal rye is gaining popularity across Illinois for its soil health and conservation benefits, but what does it mean for soybean yields? Research from the University of Illinois, funded by the Illinois Soybean Association checkoff program, is helping farmers answer that question with data-backed information.  

Led by Dr. Giovani Preza Fontes and graduate researcher Sofia Canafoglia, the study explores how cereal rye cover crops impact soybean productivity and how strategic fertilizer applications—particularly nitrogen (N) and sulfur (S)—can help farmers maintain or even boost yields. 

While cover crops like cereal rye offer clear soil and environmental benefits, many farmers have seen inconsistent impacts on soybean yield. The reason? Cereal rye can scavenge large amounts of nitrogen and sulfur, potentially creating early-season nutrient deficiencies for the following soybean crop. This research aimed to identify how fertilizer management might reduce that risk—and make cereal rye a more reliable option. 

The team conducted replicated field trials at four University of Illinois research centers: Monmouth, Urbana, Perry (Orr Center), and Ewing. Treatments compared soybeans grown with and without cereal rye, and across four fertility strategies: 

• No fertilizer (check) 

• Nitrogen alone (40 lb N/acre as urea) 

• Sulfur alone (20 lb S/acre as gypsum) 

• Nitrogen + Sulfur (40 lb N + 20 lb S/acre) 

Cereal rye was terminated 1–2 weeks before planting, and yield, soil nutrients, tissue content, and grain composition were analyzed throughout the growing season. 

Key Findings from the 2024 Season: 

• Cereal rye reduced soybean yield at most sites, particularly at Urbana and Monmouth, where wet spring conditions and delayed termination appeared to reduce soil moisture and N availability. 

• At Monmouth, nitrogen fertilizer improved soybean yield after cereal rye, helping recover about half of the observed yield loss. 

• At Urbana, an 8% yield drop was noted where rye was present, likely due to delayed planting (June 10) and reduced early-season nutrient availability. 

• At Orr, fertilizer—not rye—was the main influence on yield, but surprisingly, plots with sulfur or N+S had lower yields than those with no fertilizer. 

• At Ewing, no significant yield differences were detected across treatments. 

When averaged across all sites, the data showed that soybeans following cereal rye had reduced yields—but applying both nitrogen and sulfur helped close the gap, confirming the nutrient-scavenging effects of rye and the potential for targeted fertilizer to offset them. 

These early results suggest that when using cereal rye ahead of soybeans, N and S management may be key to protecting yield. In environments where cereal rye grows aggressively or where termination is delayed, farmers may benefit from applying supplemental nitrogen and sulfur prior to planting. 

While more data will be collected in 2025, these findings provide early guidance for those integrating cover crops into soybean rotations: 

• Terminate cereal rye early to preserve soil moisture and nutrients. 

• Monitor N and S levels, especially in high-biomass rye scenarios. 

• Consider N+S applications to reduce the yield drag and boost plant health. 

As cover crop adoption increases across Illinois, this research offers practical information to help farmers balance conservation goals with yield expectations and build more resilient cropping systems. 

For more information on this Illinois Soybean Association checkoff-funded project, visit Field Advisor’s Research Hub.  

Trial at Monmouth. Soybean around R1 growth stage.

Harvest at Urbana