Cereal rye cover crop termination at or before soybean planting has minimal effect on soybean yield across the midwestern US

Context: Interest is growing among farmers in the Midwestern US region in the potential benefits of establishing cereal rye (Secale cereale L.) as a cover crop. However, they are concerned about the implications and potential trade-offs due to this practice. Objective: We aimed to evaluate the effects of cereal rye cover crop termination at or before soybean planting on soybean (Glycine max [L.] Merr.) seed yield. Methods: Field experiments were conducted from 2019 to 2021 across 28 location-years in the Midwestern US. Treatments consisted of no cereal rye, cereal rye termination before soybean planting, and termination at planting. Cereal rye was chemically terminated at each termination timing. Cereal rye biomass and soybean yield were assessed. Results: Delaying cereal rye termination in soybean systems increased rye biomass, but its impact on soybean yield was inconsistent. Results showed that delayed termination did not reduce soybean seed yield in 25 of 28 location-years compared to a no cover crop treatment. There was no clear evidence indicating that a threshold level of cereal rye biomass accumulation reduced soybean seed yield. Conclusions: Our results suggest that farmers who adopt cereal rye as a winter cover crop in the examined region have a flexible management window for terminating cereal rye, as the timing of termination had minimal effect on soybean seed yield. However, there were no significant soybean seed yield benefits that would justify the associated cost with the use of cover crops. Therefore, conducting long-term studies in the future is highly recommended to better understand how cereal rye cover crops can influence soybean seed yield and soil quality properties over time. Further studies should also investigate the aspect of non-chemical rye management to assess its potential cost-saving effects for farmers adopting this system. Implications: These findings hold several implications for farmers, agronomists, and stakeholders. The increased cereal rye biomass due to delayed termination could offer greater soil benefits. While the inconsistent effects on soybean yield imply flexible termination options for cover crop adoption, the absence of substantial yield benefits underscores the importance of considering both short-term costs and long-term sustainability goals.