Research HighlightsSoybean–Wheat Relay Cropping is a Possible Solution for Weed Suppression
Complete the Nationwide Soybean Intensification Survey
In this article, you’ll find details on:
- A multi-regional research project explores weed suppression in soybean–wheat relay cropping systems.
- Farmers and agronomists are encouraged to complete a national survey on soybean management systems, so the research team can help meet growers’ needs.
- The project is in its first of three years, looking at planting and harvest timing, and soybean and wheat varieties that will work best together for maximum weed control.
By Carol Brown
Relay intercropping with soybeans and wheat is somewhat of an enigma in the U.S. Is this common practice in certain areas? Do farmers in other areas even know what it is?
A nationwide survey is currently active for researchers to find out answers to these questions and more. Funded by the Soy Checkoff’s multi-regional programs, the survey will inform a research team how common relay cropping is and where it’s being done in the country. This will, in turn, help scientists to address weed management within these systems.
“Intercropping systems can be used to suppress weeds. In my research, we’ve seen a tremendous benefit in weed management,” says Jason Norsworthy, Distinguished Professor and Elms Farming Chair of Weed Science at the University of Arkansas. “It allows farmers to reduce the amount of herbicide inputs and obtain a higher level of weed control. This project will use some of the learnings we’ve seen in Arkansas to expand and further the research.”
The multi-regional research is in the first year of a three-year project, with support from the North Central Soybean Research Program (NCSRP), Mid-South Soybean Board, Southern Soybean Research Program (SSRP), and the Atlantic Soybean Council.
The Soybean Intensification Survey is open to all farmers or agronomists in any soybean-producing state, and takes about 15 minutes to complete. Included in the survey are questions about general soybean management practices, use of a secondary crop such as a cover crop or another cash crop, weed management practices, as well as economic and production information.
“We want to ensure the work we’re doing is relevant to the farmers who are going to be using this information,” says Rachel Cott, assistant professor of crop science at Kansas State University. “The Intensification Survey will help the research team cast a broader net beyond farmers who are currently relay cropping. It will help us align our goals and work together to find solutions to some of the issues we’re seeing.”
The group wants to hear from soybean farmers, whether or not they use relay intercropping. The feedback can provide insights into where it’s not being done, and possibly why farmers don’t partake in this system.
The team has made the survey a state-to-state friendly competition. Cott is keeping track of where the surveys are coming from, but the rest of the provided information is kept private. She updates the leaderboard every two weeks. States with the highest response-to-soybean-acres ratio are highlighted on the online map.
“We encourage farmers to take the survey and help out their state to increase responses. Bragging rights are the reward,” Cott says.
Work After the Survey
Once the survey responses are collected, the researchers will get to work on sorting the feedback and exploring the regional differences.
“We’ll look at answers from a national perspective and things we can do in our research to better tailor this system to meet growers’ needs,” Norsworthy says. “We’ll continue to gather data in the research plots. It’s critical to have multiple years of data as each crop year is different and we want stability over several years with a system like this.”
Research plots are located in Arkansas, Illinois, Indiana, Iowa and Kansas. Each of these research locations deals with different weeds and varying amounts of weed pressure.
The team is also researching the delicate dance of wheat and soybean relay cropping through planting and harvest timing for both as well as crop varieties and maturity groups. The two crops must work together efficiently for proper canopy timing, wheat growth at soybean planting, soybean growth at wheat harvest, and herbicide application timing.
The team will take assessments of weed control and canopy coverage, weed counts and yield data for both wheat and soybeans. They will also conduct an economic analysis of this system once all the data is collected.
Intercropping Benefits
An intercropping system is a promising solution to reduce herbicide applications. Norsworthy found that intercropping reduced Palmer amaranth pressure in Arkansas through research he and his team recently conducted.
“In Arkansas, we’ll plant soybeans in early April and harvest wheat between early and mid-June,” Norsworthy explains. “At that time, the soybean plants are 12- to 18-inches tall. The wheat is cut right above the soybean plants at about 18 inches. Then we can make one application of a post-emergence herbicide with a residual and, hopefully, we’re done for the year, from a weed management standpoint.”
About two to three weeks after wheat harvest, the field will again have a canopy with the soybean crop, which is crucial for weed suppression. Without a wheat or soybean canopy, weeds – especially Palmer amaranth — continue to emerge and grow.
In addition to controlling weeds, relay intercropping can increase soil organic matter and reduce soil erosion. Non-chemical weed control can reduce opportunities for weeds to become herbicide resistant, and farmer input costs are reduced as fewer herbicide applications are needed.
The survey will be open through mid-October. The team encourages all soybean farmers to complete the survey even if they are not relay-cropping on their farms.
Published: Aug 11, 2025
The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.
