Planting Green Into Cover Crops? Learn Which Soil Residual Herbicides Can Make it to the Ground!

May 20, 2026

By Rodrigo Werle

The Wisconsin Cropping Systems Weed Science Program has been conducting extensive research on soybean “planting green” systems as part of integrated weed management strategies.

Our field research, which is part of a USB-funded multi-state project, demonstrates that planting green and terminating cereal rye when it reaches approximately 30–36 inches in height (~4,500 lbs. of biomass per acre) or at the soybean VE stage, whichever occurs first, is a promising approach for suppressing weeds without negatively impacting soybean yield (as found in UW-Madison graduate student Guilherme Chudzik’s Ph.D. research).

However, we have also consistently observed that soil-applied residual herbicides are still necessary, even in high-biomass cereal rye systems, to achieve effective early-season control of troublesome weeds such as waterhemp, according to research by UW-Madison graduate student Jose Nunes.

“The use of multiple effective soil-residual herbicides at higher labeled rates, in tandem with high cereal rye cover crop biomass, is strongly recommended to achieve more consistent early-season weed control and to reduce selection pressure for further herbicide resistance,” said Dr. Rodrigo Werle, University of Wisconsin-Madison

A common question from stakeholders across Wisconsin and beyond is: Which soil residual herbicides are compatible with high-biomass cereal rye cover crop systems?

In other words, which herbicides are most likely to move through the cereal rye residue layer and reach the soil where they can be effective?

To address this, WiscWeeds students and staff Lukas Holderby, Sabeel Abuhakmeh, and Dr. Ahmad Mobli conducted a controlled-environment study this winter evaluating 21 single-active-ingredient corn and/or soybean herbicides. This study assumed adequate precipitation following application and simulated a condition of ~4,500 lbs. of dry cereal rye per acre on soil surface. (Future research will evaluate how rainfall patterns influence herbicide movement through cover crop residue.)

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Video: Root Exudates, Soil Biology, and How Plants Recruit Microbes | Field Talk Friday

Field Talk Friday | Dr. John Murphy | Root Exudates, Soil Biology, and How Plants Recruit Microbes

Most of us spend our time managing what we can see above ground—plant height, leaf color, stand counts, and yield potential. But the deeper you dig into agronomy, the more you realize that some of the most important processes driving crop performance are happening just millimeters below the surface.

In this episode of Field Talk Friday, Dr. John Murphy continues the soil biology series by diving into one of the most fascinating topics in modern agronomy: root exudates and the role they play in shaping the microbial world around plant roots.

Roots are not passive structures simply pulling nutrients out of the soil. They are active participants in the underground ecosystem. Plants constantly release compounds into the soil—sugars, amino acids, organic acids, and other molecules—that act as both energy sources and signals for soil microbes.