Don't Miss Optimal Cover Crop Opportunities

WSSA-member scientists extol benefits from proper establishment in grain-crop systems

WESTMINSTER, Colo., Sept. 24, 2026 /PRNewswire/ -- If timed right, establishing a fall cover crop can provide far more than just improved weed control next season, report leading Weed Science Society of America (WSSA) cover-crop researchers. Other potential benefits include reduced herbicide and nitrogen costs, reduced soil erosion, and less difficulty managing multiple herbicide-resistant weed species, such as Palmer amaranth, waterhemp and horseweed.

"If farmers achieve their weed suppression goals, they will almost certainly realize other benefits along the way, such as improvements in soil health," says Michael Flessner, Ph.D., Professor and Extension Weed Science Specialist, Virginia Tech, and current WSSA Weed Loss Committee Chair. "For example, farmers planting legume cover crops may be able to reduce nitrogen fertilizer inputs. Thus, cover crops can be way more than just a weed management tool."

However, it's important to establish the right crop cover at the optimal time for the intended grain crop system. "Wait too long to plant, and the cover crop may not have enough time to establish – especially for less winter hardy species," he points out. "For higher-level goals such as weed suppression or reducing fertilizer inputs, a high biomass cover crop is needed in the spring. That biomass starts in the fall."

John Wallace, Ph.D., Associate Professor, Pennsylvania State University, agrees. "Fall-sown winter cereal cover crops, like cereal rye, have the greatest utility as a weed management tool in grain crop systems," he says. "However, from a weed control perspective, it is important to establish cover crops as early as possible in the fall to ensure good stand establishment and increase biomass potential."

Wallace, who currently serves on the WSSA Science Policy Committee, adds that recent survey results from the Conservation Technology Information Center (CTIC) and Getting Rid of Weeds Through Integrated Weed Management (GROW) show "the benefits of cover crops are not just being realized in research plots. Farmers who have adopted the practice are also seeing these results on the farm, and at commercial scale."

Still, Flessner cautions that cover crops require a higher level of management than winter fallow cropping systems. "For benefits to be realized, the farmer must be both willing to put in the work as well as have the knowledge," he says. "GROW's Farmer Forums on cover crops are a great example of farmers sharing their knowledge and experience directly with other farmers, likely leading to greater adoption and success with this practice."

Northern grain-growing regions can benefit from cover crops as much as southern growing regions can, if established soon enough in September or October – or by delaying spring termination, says Rodrigo Werle, Ph.D., Associate Professor and Extension Cropping Systems Weed Scientist, University of Wisconsin–Madison. He advises checking recommendations from the nearest land-grant university and/or experienced local farmers and crop advisers for those cover-crop planting and termination recommendations.

"Corn-soybean rotations dominate much of the Midwest, making the period immediately following harvest a critical window for cover crop establishment," he says. "Winter-hardy species such as cereal rye are particularly valuable, because they establish in the fall, overwinter, and resume growth in the spring. That spring growth allows substantial additional biomass production before termination and establishment of the next cash crop. In our research, we have consistently learned that simply having a cover crop is not enough: biomass matters when weed suppression is the goal."

Werle, who currently serves as an Associate Editor for WSSA's online journal, Weed Technology, adds that planting soybean green next spring (seeding soybeans into a standing green cover crop) has shown to be one successful way to extend the cover crop growing period to achieve the needed biomass for optimal cover-crop benefits. When planting green, the crop cover can be terminated either at planting or shortly thereafter using a roller-crimper or herbicide.

"Our work across 14 universities has shown that planting soybean green can extend the cover crop growing period, substantially increase biomass production, and improve suppression of waterhemp and Palmer amaranth when integrated with effective herbicide programs," he says. "One of the most important lessons from this work is that cover crops should not be viewed as a replacement for herbicides, but rather as an additional effective tactic within an integrated weed management program. By reducing the number and size of weeds exposed to post-emergence herbicides, cover crops can help improve herbicide performance and stewardship."

For more information about WSSA and its weed management and herbicide resistance resources, visit: https://wssa.net/projects/herbicide-resistance/.

About the Weed Science Society of America 
The Weed Science Society of America is a nonprofit scientific society, founded in 1956 to encourage and facilitate the development of knowledge concerning weeds and their impact on the environment. The Society promotes research, education and extension outreach activities related to weeds, provides science-based information to the public and policy makers, fosters awareness of weeds and their impact on managed and natural ecosystems, and strengthens cooperation among weed science organizations across the nation and around the world. For more information, visit www.wssa.net.

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SOURCE Weed Science Society of America