Key Takeaways
- A new study published in Weed Science, a journal of the Weed Science Society of America (WSSA), found that higher cereal rye cover crop seeding rates improve weed suppression in organic no-till soybean production.
- The two-year study examined field experiments from the 2021-2022 and 2022-2023 growing seasons at Penn State's Russell E. Larson Agricultural Research Center near Rock Springs, Pennsylvania.
- Researchers tested four rye seeding rates (0.5 to 3 bushels per acre), two sowing arrangements, and fall-applied poultry litter at varying rates alongside two soybean planting dates.
- Higher rye seeding rates reduced weed biomass significantly more than lower rates, without affecting soybean yield or rye biomass itself.
- In one of the two seasons studied, planting soybeans into living rye (“planting green”) reduced soybean establishment and yield.
Weed Science Society of America Study Finds Higher Rye Seeding Rates Cut Weeds
A study published in Weed Science, a journal of the Weed Science Society of America (WSSA), found that a cereal rye cover crop helps reduce weed pressure in organic no-till soybean production, particularly when seeded at higher rates. The two-year study reviewed field experiments conducted during the 2021-2022 and 2022-2023 growing seasons near Rock Springs, Pennsylvania, at Pennsylvania State University's Russell E. Larson Agricultural Research Center.
Weed Science Society of America Study Design and Methodology
The researchers ran two experiments to evaluate rye cultural management strategies for rye biomass, weed suppression and soybean yield. The first tested four rye seeding rates, ranging from 0.5 to 3 bushels per acre, alongside two sowing arrangements — grid versus row sowing. The second tested fall-applied poultry litter at 0, 1.5 and 3 tons per acre, combined with two soybean planting dates: planting green into living rye or standard planting after rye termination.
“The aim of this study was to compare the magnitude of weed control and soybean yield under different cereal rye densities within the soybean phase of cover-crop based organic rotational no-till production,” said Laurel Wellman, a Ph.D. student in plant sciences at Pennsylvania State University and the study's corresponding author. “Our results indicated that all cereal rye seeding rates reduced weed biomass compared to the unseeded cereal rye control plots, and that the higher cereal rye seeding rates reduced weed biomass significantly more than the lower seeding rates.”
Key Findings on Weed Suppression and Soybean Yield
According to the study, increasing the cereal rye seeding rate did not lead to increased rye biomass but did increase weed suppression. Soybean yield was unaffected by rye seeding rates, and sowing arrangement did not affect any measured response. While fall-applied poultry litter significantly increased rye biomass, it did not improve weed suppression.
“Increasing cereal rye seeding rate did not lead to increased rye biomass but did increase weed suppression. Soybean yield was unaffected by rye seeding rates, and sowing arrangement did not affect any response,” said Wellman.
Limitations and Practical Implications
During one of the two cropping seasons studied, planting green reduced soybean establishment and yield. The researchers said this highlights the limitations of organic no-till soybean production within grain crop rotations in the Northeastern U.S. when cereal rye is used as a stand-alone weed suppression method. They noted that increasing cereal rye seeding rates or applying fall fertility could serve as effective cultural practices when combined with other weed control tactics to supplement suppression from rye surface mulch. Overall, Wellman said the study “indicates that higher cereal rye seeding rates improved weed suppression independently of cereal rye biomass.”
The research, titled “Cultural management of cereal rye for weed suppression in cover crop-based organic rotational no-till soybean,” was published in Weed Science, a Weed Science Society of America journal produced by Cambridge University Press.
