Just beans and cornTwo-crop rotation has pros and cons.
By: Jonathan Knutson, Agweek
In 2012, for the first time, Kulm, N.D., farmer Bart Schott grew only corn and soybeans on his family farm. He had raised spring wheat, too, but he and his son, Andy, decided to focus on more profitable corn and beans.
“We jumped into it with the thought of staying in, and we haven’t looked back,” Bart Schott, a former president of the National Corn Growers Association, says of the corn-soybean rotation.
While there are advantages to rotating three crops, Schott says, farmers need to ask themselves, “How much of that third crop can we raise and still keep the farm profitable?”
In contrast, Mike Faught, an Absaraka, N.D., farmer who raises wheat, corn and soybeans, says he’s sticking with a three-crop rotation.
“There are advantages to the third crop,” he says. “It isn’t just dollars per bushel and bushels per acre. There’s a lot going on behind the surface.”
The decision that Schott and Faught already have made is one that many farmers across the Upper Midwest continue to ponder this winter.
Go with the obvious financial advantages of a two-crop rotation? Or stick with the sometimes-subtle benefits of three or more crops?
In a corn-soybean rotation, a farmer rotates the two crops annually over a two-year period.
In a three-crop rotation, a farmer rotates three crops annually over a three-year period. Typically, in much of the Upper Midwest, wheat or another small grain is the third crop in a rotation with corn and soybeans.
A rotation of only corn and soybeans, a staple of the Corn Belt for decades, is increasingly common in the Upper Midwest, too. Attractive corn and soybean prices, combined with new corn varieties suitable for the Northern Plains, have led some farmers to bump small grains from their rotation and go with just corn and beans.
There aren’t reliable statistics of how many acres are in a corn-soybean rotation, but Joel Ransom, small grains and corn agronomist with the North Dakota State University Extension Service, estimates the number in North Dakota may have doubled in the past five years.
Advocates of the corn-soybean rotation say they can make more money with just two crops without sacrificing soil health.
Others, including some experts familiar with corn-soybean rotations in the Corn Belt, say rotating three or more crops makes a lot of sense.
“There’s nothing wrong with corn and soybeans. It works. But any time you can keep diversity, it’s a good thing,” says Joe Lauer, a University of Wisconsin-Madison agronomist who has worked with a number of producers who raise only corn and soybeans.
Matt Leibman, an agronomy professor at Iowa State University and its Wallace Chair for Sustainable Agriculture, says a growing amount of research identifies benefits of rotating three or more crops.
The advantages include:
• Spreading out the workload. Small grains are planted and harvested at different times than corn and soybeans.
• Improving risk management. Having a variety of crops can reduce the overall damage from a stretch of bad weather.
• Potentially reducing input costs.
• Managing herbicide resistance in weed management. “Long rotations can give you an outstanding means of addressing weed management,” Leibman says.
• Enhancing soil health and reducing danger from crop disease and insects.
“The more you can keep different crops in a rotation, the better off you are. When you get to a monoculture, which is continuous corn or even corn and soybeans, there’s more and more pressure on the cropping systems. Bugs and critters will evolve to deal with that,” Lauer says.
Continuous corn is planting corn on the same field year after year.
•Improving overall yields.
“A corn-soybean rotation certainly works. But our data shows, whenever you have three or more crops in a rotation, it benefits all the crops in that rotation,” Lauer says.
Adding a third crop such as wheat can raise yields of corn and soybeans in the years the latter two are grown. The question is, however, whether those additional yields produce enough income to offset lower income in the year in which the third, less-profitable crop is raised.
For instance, a corn-soybean rotation is increasingly popular in southeast North Dakota, where Schott farms. That reflects the relative price and profitability of corn, wheat and soybeans.
Going into the 2013 growing season, NDSU projected that farmers in southeast North Dakota would achieve a return of $196.69 per acre with corn, with soybeans returning $143.98 per acre and wheat returning $108.75.
The numbers were only projections and, in any case, will change substantially in the 2014 growing season. But they indicate why a rotation of corn and soybeans can be more attractive financially than one with wheat, corn and soybeans.
Corn prices have slumped, which, on the surface, would seem to limit interest in a corn-soybean rotation.
But other commodity prices have dropped, too. That increases the difficulty of turning a profit in 2014, creating more incentive to plant the most-profitable crops, experts say.
Study shows benefits
A rotation of just corn and soybeans hasn’t always been popular, even in the Corn Belt.
Though corn has been common since the 1930s, soybeans have been around only since the late 1970s and early 1980s in much of the Upper Midwest, Lauer says.
“Soybeans are a relatively new kid on the block. It’s only in the last generation that corn-soybean has become the norm,” he says.
Now, researchers are studying what Leibman calls “productivity limitations” of a corn-soybean rotation.
Leibman led a 2012 study by Iowa’s Leopold Center for Sustainable Agriculture that examined a decade of research into corn-soybean rotations and diverse rotations.
The study found that a diverse rotation on average produced 4 percent higher corn yields and 9 percent higher soybean yields.
The higher yields were achieved by replacing purchased inputs with “combinations of ecological processes, human knowledge, production management and skills,” according to the study.
Yields remain high even in the years of transition from corn-soybean rotations to diverse rotations, the study says.
Yields also remain high regardless of whether GMO or non-GMO crops are used, the study says.
Other benefits identified by the study:
• Synthetic nitrogen use reduced by 80 to 86 percent.
• Effective weed control with 88 percent less herbicide.
• Herbicide-related freshwater toxicity 200 times lower after nine years.
More information can be found at www.leopold.iastate.edu.
Diversity still popular
It’s unlikely that a corn-soybean rotation ever will become the norm across the western Dakotas and northwest Minnesota, where the climate is well-suited to wheat and other crops, experts say.
“You have such a tradition of diversity,” Lauer says to farmers in the region.
Longer, more diverse rotations are common in central South Dakota, says Ruth Beck, Pierre-based agronomy field specialist with the South Dakota State University Extension.
“There’s just a lot of diversity here. People tend to have more four-year rotations,” she says.
Wheat’s growing window is different from that of corn and soybeans, which helps spread risk, she notes.
In 2012, for instance, farmers in her area who grew wheat generally had good yields, despite drought. However, the dry conditions hurt corn and soybeans, she says.
Faught farms in North Dakota’s Cass County, the nation’s leading soybean producer. Corn is increasingly common in the county, usually at the expense of wheat.
Continuing to grow wheat, along with corn and soybeans, enhances soil fertility and raises yields of all three, he says.
Ideally, Faught says, farmers should be considering a five- or six-year rotation.
“I don’t know if anybody will be doing that, though,” he says.
“There are just so many things to consider” in deciding the length of a rotation, he says.
No simple answers
Lower corn prices will encourage some farmers who had been planting only corn on a field to switch to soybeans in 2014, Leibman says.
Ransom, of the NDSU Extension Service, says a corn-soybean rotation is “far superior” to continuous corn.
But he says he doesn’t have any easy answers about the wisdom of a corn-soybean rotation versus a rotation of more than two crops.
“On one hand, farmers have been doing corn-soybeans for decades, with a fairly high level of success and apparent sustainability,” he says.
“We haven’t seen any significant train wrecks because of narrower rotations,” he says. “I haven’t seen any real evidence that we’re harming the soil by not having more than two crops.
“I’m not telling people, ‘Don’t do corn-soybeans because it’s nonsustainable.’ There’s evidence it’s working,” he says.
On the other hand, “If people do diversify, there are some benefits, as far as weed control and timeliness of operations,” he says.
“But the challenge is finding a third crop that becomes as profitable as corn or soybeans,” Ransom says.