by Kacey Birchmier
Think of a few dynamic duos. Batman and Robin. Thelma and Louise. Bonnie and Clyde. Add one more to that list: corn and soybeans.
Iowa farmers plant about 10 million acres of soybeans, alongside 13 million to 14 million acres of corn. Soybeans are considered the perfect complementary crop to corn, but that wasn’t always the case.
“Originally, soybeans were brought to the U.S. as a forage crop, not a grain crop,” said Mark Licht, Iowa State University Extension and Outreach cropping systems specialist.
A mix of forces — including global protein demand, shifting economics and policies, and major advancements in breeding — paved the way for soybeans.
Early years
As pastures, small grains and hay began to fade from the landscape, soybeans gained acreage.
“The Iowa farm facilitated this change happening,” Licht said. “As we started using tractors, we no longer needed horses, so we didn’t need small grains, hay and pasture to feed those horses.”
In the early 1900s, most farms had a variety of livestock, but farms shifted to specialization and feed rations that rely on soybean meal and corn, he said.
World War II also helped push soybeans from being just a forage crop. As trade was disrupted, acreage began to increase.
“It helped establish the crop more widely in Iowa and the U.S., because they needed soybean oil and the meal,” said Matt Smalley, Corteva Agriscience data science and engineering lead.
Ying and yang
“Soybeans make a nice rotation crop,” said Paul Stephens, a retired soybean senior research director at Corteva Agriscience. “There’s a plurality, where each crop helps the other. The bottom line is that overall crop health is improved, and yields are higher in the rotation.”
Licht said soybeans’ flexibility helps them thrive in conditions other crops may not, such as in heavy residue after a corn crop.
“Soybeans are an adaptable crop, especially indeterminate soybeans, as they have inherent tolerance to stress,” Smalley explained.
Management benefits reinforce the duo. Corn grown after soybeans requires a smaller amount of nitrogen to be applied.
“Soybeans produce some amount of N that can be used by the corn crop, so that’s also complementary,” Smalley said. “It reduces input costs for the following corn crop.”
Rotating the two provides natural pest control because they share few insects or disease issues, breaking several pest cycles.
Another advantage is equipment compatibility, as planting and harvesting require minor tweaks.
“There may be differences like row spacing, but corn and soybeans make the best use of the farmer’s investment in equipment,” Smalley said.
Markets and profitability
Strong domestic demand from livestock to biofuels helped cement soybeans in the Midwest.
“Soybeans, generally speaking, have a market and profitability in Iowa and across the Midwest,” Licht said. “We have some markets for small grains, but they’re small, limited markets. We’re not going to displace millions of acres of corn or soybeans for these other crops.”
Policy and breeding
Dean Podlich, Corteva Agriscience research and development digital seed lead, pointed to the U.S. Plant Variety Protection Act of 1970 as having a significant influence on soybeans’ future.
“Before that, a lot of the investment was done through universities, and the intellectual property couldn’t really be protected,” Podlich said. “There was no encouragement for private industry to get into soybean.”
“After the IP [intellectual property] of seed improvement could be protected, companies invested in industry plant breeding, and that’s when you can see a nice increase in yields,” Smalley said.
Pioneer started its breeding program in 1973 and later that year acquired Peterson, a company with an established breeding program. It leveraged technological advances, whether it be phenotyping, analytics or genotyping, and applied those processes to soybean breeding.
Pests like soybean cyst nematode, phytophthora and sudden death syndrome were managed through the first uses of molecular breeding.
“That really helped stabilize yields and provide a basis of disease tolerance that then allowed us to increase yields over the last 20 years,” Smalley said.
It used to take 10 years to bring a variety to the market; now, it’s seven years. Breeding significantly advanced compared to when Stephens started at Pioneer in 1993.
By “utilizing markers, we could ensure that only plants with needed traits would be advanced,” Stephens said. “We were no longer carrying non-traited material through the program. Prior to marker-assisted breeding, it was a challenge to increase yield while adding defensive traits.”
Podlich said the coevolution of genetics with management practices resulted in improved yields, pointing to gene editing.
“This is going to be just as, if not more, transformational as genetically modified traits,” he said.
Birchmier writes from Maxwell in central Iowa.