Weed Control Programs: Evaluating Liberty Ultra in Dicamba-resistant soybeans
Liberty Ultra represents a newer glufosinate formulation designed to improve weed control and application flexibility. This project evaluates how Liberty Ultra performs within dicamba-tolerant systems and how it can be best positioned for maximum effectiveness.
Herbicide resistance continues to be one of the most significant challenges in South Carolina soybean production, particularly with widespread resistance in Palmer amaranth populations. As traditional herbicide programs become less effective, growers must rely on alternative chemistries and integrated approaches to maintain effective weed control.
Glufosinate-based systems have become increasingly important in managing resistant weeds, and Liberty Ultra represents an advancement in this technology. With improved formulation characteristics, Liberty Ultra is designed to enhance weed control, optimize application efficiency, and provide more consistent performance under a range of field conditions.
This project was conducted to evaluate the performance of Liberty Ultra within dicamba-tolerant soybean systems and to identify best management practices for maximizing its effectiveness under South Carolina growing conditions.
Methods
Field trials were established using standard soybean production practices, with applications made at multiple timings to target weeds at different growth stages.
Treatments included Liberty Ultra compared alongside standard glufosinate programs, as well as integration with dicamba-based systems.
Emphasis was placed on controlling Palmer amaranth, one of the most problematic and economically damaging weeds in the region.
Weed control evaluations were conducted throughout the growing season, focusing on control efficacy, speed of activity, and consistency across treatments.
Crop response was also monitored to ensure that herbicide applications did not negatively impact soybean growth or development.
Results
Results showed that Liberty Ultra provided effective weed control when applied under optimal conditions, particularly when used as part of a multi-pass, integrated program.
However, performance was highly dependent on:
application timing
spray coverage
and environmental conditions at the time of application.
Programs that relied on a single application were less consistent, reinforcing the need for a program-based approach. Future work will focus on refining recommendations and expanding evaluations across environments.
As a result of this project, researchers confirmed that Liberty Ultra is an effective tool for post-emergence weed control in dicamba-tolerant soybean systems, but its success depends heavily on proper use. Integrating Liberty Ultra into a comprehensive weed management program—including residual herbicides and multiple modes of action—remains essential for long-term control and resistance management.
This information is from the 2025 research project, Evaluation of Liberty Ultra in Dicamba-Tolerant Soybeans. The lead was University of Clemson researcher Dr. Michael Marshall. Project sponsored by the South Carolina Soybean Board.
