(Photo: Iowa Soybean Association / Joclyn Bushman)
Insights from relay cropping in 2024
January 23, 2025 | Kriss Nelson
The goal of Iowa Soybean Association’s (ISA) relay cropping work is to boost farmer income and enhance soil health.
“Relay cropping is the chance to combine some economic gains with the environmental benefits of raising an overwintering cereal grain,” says Alex Schaffer, ISA senior research agronomist.
In relay cropping, an overwintering cereal grain is planted in the fall; soybeans are then planted within the cereal grain in the spring. Cereal grains are harvested in July, while soybeans mature for the rest of the growing season and are harvested in the fall.
Schaffer shared insights from 2024 relay cropping trials conducted by ISA’s Research Center for Farming Innovation (RCFI) during an Iowa Learning Farms conservation webinar last week.
“It is really important for ISA to be involved with this work and the Iowa Learning Farms really values this partnership,” says Matt Helmers, director of the Iowa Nutrient Research Center and a professor in the Department of Agricultural and Biosystems Engineering at Iowa State University. “While this practice may not be economical or viable everywhere, as cover crop seed needs grow, this could be a way for producers to add some value to their operation, so it is essential we continue to do research and demonstration on this potential cropping system.”
In addition to their own trials, RCFI collaborated with Iowa Learning Farms on statewide relay cropping trials. Except for one trial using wheat, Schaffer reported all trials used cereal grain.
ISA’s 36 relay cropping trials (since 2020) show the practice requires specific management, is risky and is impacted by geography and rainfall.
Why is there interest in relay cropping?
Potential farm benefits for relay cropping include:
- On-farm cover crop seed production
Environmental benefits of relay cropping include:
- Improved water infiltration
“Environmental benefits and farm benefits, I think it is important to call out the two are not mutually exclusive,” says Schaffer. “Things that benefit the environment usually benefit the farm, especially for soil health and erosion prevention.”
Market expansion for cereal grains is crucial for the adoption of this practice.
“The systems are most profitable when there is the option to market the small grain as a cover crop seed,” says Schaffer. “There needs to be some sort of marketplace in the state of Iowa for the small grain if this is going to be a practice that takes off.”
Considerations for relay-cropped small grains
Preliminary research shows that planting by the first half of October allows growers to reduce small grain seeding rates.
Schaffer says according to data provided by Iowa State University, seeding rates of 25, 50 and 75 pounds per acre did not show a yield loss when planted by Oct. 15.
Plans are made for research on small grain seeding rates will continue.
Other factors to consider include:
Row indexing is the distribution of plants within a row and could be the biggest key from a plant physiology perspective.
“Row indexing, I think is one pathway to success when relay cropping,” says Schaffer. “Whether this means plugging a row in the air seeder or planter – just to make a place to plant some soybeans and give them some room to grow seems to be helpful,” says Schaffer.
Soybean management in relay cropping
Maturity matters
“Just as it does in a conventional soybean system, later the maturity soybeans seem to yield better and may be amplified in a relay cropping system,” says Schaffer.
- Seeding rate greater than 120,000 soybean seeds per acre
Schaffer says when planting shorter-maturity soybeans, they benefited from a higher seeding rate.
“Preliminary data says seeding rates greater than 120,000 may be beneficial, maybe even closer to 150,000,” he says. “Consider planting more soybean plants because each one of those plants will be under more stress and could produce fewer seeds, and you could offset that by planting a higher population. More work needs to be done in this area.”
- Early soybean planting before the small grain is jointing
“Try to avoid damage to small grains and this will get the soybeans planted and growing before the small grain is too competitive,” says Schaffer.
“If you can’t row index because you are spreading or broadcasting the cereal rye, strip till before planting soybeans could be beneficial,” says Schaffer “Just anything to give the soybeans more room to grow.”
Relay cropping research continues
In 2025, Schaffer’s statewide relay cropping research will include five locations to study wheat.
“We will continue researching this practice,” he says. “We have seen it fail, but we have seen some success. There is that chance for profitability and conservation benefits and the fact it is done with soybeans is really why we are interested in learning more about relay cropping.”
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