It starts with the soybean seed
Bill Backhaus leads off every agronomy training session he conducts with this question: “What’s the most important factor in soybean production?”
“Everybody has their own opinion, and I get a lot of different answers,” says the BASF seed agronomist. “Some say weed control. Others will bring up row spacing or diseases. But at the end of the day, the most important thing is variety selection and genetic potential.”
Other factors are important, but genetic yield potential lies at the core, he says. An average difference of 12.1 bushels per acre between the highest- and lowest-yielding soybean variety surfaced in 2014 to 2020 Iowa Crop Performance Tests conducted by the Iowa Crop Improvement Association and Iowa State University, Backhaus adds.
“We have to get out of the fallacy of selecting varieties first based on weed control and herbicide-tolerant traits,” Backhaus says. Excellent herbicide-tolerant trait technologies exist, but farmers should first focus on genetics and agronomics when selecting varieties, he says.
One quandary farmers face when selecting soybean varieties is which maturity group to choose. On average, longer-maturing soybean varieties have potential – but no guarantee – to yield more than shorter-maturing ones, says Shawn Conley, University of Wisconsin Extension agronomist. In any given year, though, soybean yields between varieties with one maturity group (MG) difference – such as between MG 1.5 and MG 2.5 – can yield the same, he adds.
Kelly Garrett has followed this lead in backing away from planting MG 3.0 beans that he used to plant where he farms near Arion in west-central Iowa. He planted MG 1.7 to 2.7 soybeans in 2020 with no decreased yield potential.
“Last year, the MG 1.7 beans actually yielded the best,” he says. “I plan to plant some MG 1.4 beans this year.”
He also teams earlier-maturing soybeans with early planting, which started April 8 in 2020. “Planting early beans gives a great opportunity to build a bigger [photosynthesis] factory,” he says. Ultimately, increased photosynthesis translates into higher yields, he says.
There’s also a marketing reason for planting early soybeans.
“I harvest early in September and get a basis opportunity,” says Garrett. “Last year, it was a 30¢ to 50¢ [per bushel] above basis when I harvested, and two weeks later it was 50¢ under. There are also no lines in the elevator.”
Early harvest also enables Garrett to plant winter wheat on a share of those soybean acres following harvest. It also means he harvests in better weather, rather than fight colder and often rainier weather later in the fall.
“Every day spent harvesting in September is worth two days in November,” he says.
Iron Deficiency Chlorosis
Pairing genetic potential with defensive characteristics is paramount. Those qualities are needed to tackle maladies such as iron chlorosis, which particularly plagues farmers in the Upper Midwest. High-yielding varieties susceptible to iron deficiency chlorosis (IDC) are riddled with the malady’s calling card of chlorotic leaves and stunted plants.
“It not only hampers yield, but it can also delay soybean canopy,” says Steve Carlsen, Levesol and crop enhancement manager for CHS Agronomy. “IDC delayed canopy can create some of the worst weed scenarios in those iron chlorosis fields.”
In west-central Minnesota, farmers were ready to scuttle soybeans and plant more corn due to IDC. That’s changed, says Harmon Wilts, a DeKalb/Asgrow technical agronomist. “We now have some varieties that can better tolerate iron chlorosis,” he says.
Variety selection, though, is just one way to manage IDC. Drainage is another.
“We tend to have high-pH soils and high carbonates that contribute to iron chlorosis, and you can’t do much about them,” says Wilts. “The third factor is high salt content in our soils. If we install tile that doesn’t let the water table rise and bring all the salts with it, it decreases the incidence of iron chlorosis.”
Another tool farmers use to help manage IDC are iron chelate fertilizers – such as Soygreen – applied in the form of seed-placed and in-furrow treatments. They enable plants to take up iron from the soil to overcome iron chlorosis, Carlsen says.
Such treatments have a proven track record, says Carlsen. However, they can range in cost from the low $20s to $30 per acre. Field areas afflicted by iron chlorosis tend to be spotty. This can sync with the use of precision agriculture tools to help ensure the right acres are treated.
“Variable-rate maps that show these areas are hugely beneficial,” says Carlsen. “They’re a way to better manage product placement and help growers maximize their results.”
Putting It All Together
Gleaning 80-bushel-per-acre soybean yields is great, but there’s a price to be paid the following year. “Pulling off yields like that will impact nutrients, especially potassium,” says Tammy Ott, a Nebraska-based Channel technical agronomist. “That’s a big one that needs to be managed as we take off these big soybean yields.”
“Whether broadcast or in-furrow, fertility is an investment,” adds Carlsen. “You’re building a nest egg for future crop production.”
Each soybean management component adds up, says Mark Storr, a BASF technical services representative.
“Just one three-bean pod on every soybean plant can mean an extra 3 bushels per acre,” Storr says. “Whether it’s a seed treatment or a weed-free field, or a fungicide, you can get more of those three-bean pods on plants through those practices.”
Soybean Gall Midge Stalks Soybeans
A pest recently surfaced to torment soybean farmers. The soybean gall midge has been damaging soybeans in areas of Nebraska, Iowa, and South Dakota. Midge larvae feed inside the plant tissue and weaken plants.
“We see some issues in September with standability or lodging,” says Tammy Ott, a Channel technical agronomist. The good news is that so far, most feeding is limited to the edge of fields, with damage decreasing inside the field.
Entomologists are studying the merits of insecticide application and planting date, says Ott. There may also be a varietal solution on the way.
BASF is evaluating current and future lines for natural soybean gall midge tolerance. In one location near Griswold, Iowa, BASF tested 31 varieties ranging in relative maturity groups from 1.4 to 3.9. Each variety was replicated 14 times, and one variety showed increased native tolerance to soybean gall midge in each replication, says Bill Backhaus, BASF seed agronomist. However, more trials will be needed to further test potential varietal tolerance, he adds.