Reevaluate your soybean strategy for 2021

If one word sums up how to approach the 2021 growing season, it’s this: reevaluate.

That’s because 2020 was such an anomaly, with COVID-19 hanging over farmers as they planted and grew their crops, says Ryan Wolf, WinField United agronomy services manager. Drought also coincided with COVID-19 over much of the year in many areas. Some areas like northwest Iowa received just 3 inches of rain after July 4. 

“That’s not a lot of moisture to sustain a crop,” Wolf says.  

The good news is that the 2020 growing season is drawing to a close as 2021 beckons. 

“2020 was a year of getting by,” Wolf says. “So now is the time for farmers to reevaluate whether their plan worked or if they missed their yield potential.” 

Here’s how.

Ryan Wolf of Winfield United
Photo credit: Winfield United

Variety Selection 

“This was a tough, tough spring for us,” says Jason Harmon, an Indiana-based DeKalb/Asgrow technical agronomist. “It was cold and dry in April, and cold and wet in May.”

This complicated a trend in areas like north-central Indiana of farmers planting soybeans early at the same time as corn, says Harmon. “More farmers are planting later-maturing corn and early-maturing beans at the same time,” he says. Come harvest, this enables them to fully concentrate on harvesting soybeans before moving to corn.

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 MG, can yield the same, he adds. 

“Variety selection heavily based on maturity group is not a silver bullet for frequently increasing yield,” he says. 

Jason Harmon
Exceptions exist. Farmers may want to devote a portion of their acres to longer-maturing varieties to capture any extra yield potential. Still, Conley advises farmers to pick varieties based on a realistic maturity group for their region, planting date, local and regional performance, and diseases present in their fields. 

Late August rainfall can help maximize yields of later-maturing varieties, adds Harmon. 

“This year in north-central Indiana, it was hot and dry for the first part of August, and that did not favor early-season beans,” he says. Meanwhile, later-
maturing varieties that were still putting on pods and seed size could better benefit from rains in late August, he says. 

“We advise spreading the risk, planting some Group 2s and also some Group 3s in the event August rains come,” says Harmon.  

Dicamba

“There was never a year like 2020 with soybean varieties,” says Wolf. Part of it was spurred by a June 3 opinion by the U.S. Court of Appeals for the Ninth Circuit that vacated the Environmental Protection Agency’s 2018 conditional registration of XtendiMax, Engenia, and FeXapan dicamba herbicides for dicamba-tolerant soybeans.

“The whole dicamba picture became unclear when farmers wondered if they could even spray it,” says Wolf. “Then you had Enlist [featuring 2,4-D choline tolerance] beans and LibertyLink GT27 beans, with XtendFlex beans coming [tolerance to glyphosate, glufosinate, and dicamba for 2021. 

“There are just so many choices and a lot of confusion in the marketplace,” he adds. “I think we’re really going to have to study plot data and select the beans first on an agronomic basis, instead of spraying Enlist [Duo or One] and then picking varieties because it looks easier [supposedly to some farmers] than spraying dicamba. It comes back to doing your homework for 2021.”

Defensive Traits 

Drought had at least one bright spot in 2020. In most areas, disease didn’t clip soybean yields like in 2019.

“For soybeans, white mold is a big disease,” says Harmon. “But this year, it wasn’t as bad.”

Varieties that tolerate white mold helped. “Some varieties fend it off better than others,” he says.

If white mold snaps back in 2021, fungicides are another tool farmers can use. Control, though, can hinge on timing the fungicide to penetrate into the canopy. Daren Mueller, Iowa State University Extension plant pathologist, recommends applying a fungicide to manage white mold at or close to the R1 flowering stage. 

Frogeye leaf spot is another disease that has migrated into the Midwest from the Mid-South. “Normally, we focus on genetics to manage it,” says Harmon. “But fungicides have also come into play with great results.”

Yield potential can still be salvaged with a triazole (Group 3) fungicide, says Dean Grossnickle, a central Iowa agronomist for Syngenta. However, relying on one mode of action has caused frogeye leaf spot to resist strobilurin fungicides, says Grossnickle. That’s why including both a triazole and SDHI (Group 7) fungicide is recommended. Fungicide works best when applied at the R3 beginning pod stage, he says.

Rotating with corn is another way to beat these diseases, says Harmon. Still, rebounding soybean prices may spur some farmers to plant soybeans on soybeans. This, though, heightens the potential for disease. Depending on field history, it highlights the importance of selecting varieties that resist familiar diseases like white mold and frogeye leaf spot in addition to diseases like brown stem rot and stem canker, says Harmon. 

Insects

Insects are another 2021 concern. “A big one we have is bean leaf beetle,” says Harmon. “Its first generation comes during the early first and second trifoliate stage, and can wreak havoc. It lays its eggs for the next generation that hatch about R3 [beginning pod], and then feeds on the leaves and stems before going after the pod walls. A insecticide with strong residual applied during R3  can knock them out.”

Volunteer Corn Surprise

Volunteer corn in a mature soybean field
Photo credit: Gil Gullickson
August 10’s derecho that tore through Nebraska, Iowa, Illinois, Indiana, Wisconsin, and Michigan was bad; it destroyed crops and ravaged bins. Soybean producers may be reminded of it next year when planting soybeans on affected 2020 cornfields because of volunteer corn.

Besides competing for water and nutrients, the volunteer corn can provide a haven for corn rootworm beetles to lay their eggs, says Randy Niver, an Illinois-based technical agronomist for DeKalb/Asgrow. 

Normally, rotating corn with soybeans spurs rootworm larvae to die. Not so with volunteer corn.

“Rootworm beetles can lay eggs in volunteer corn, just as in actual cornfields,” he says. If corn is planted in 2022, eggs could hatch and the larvae feed on roots. Adding herbicides like clethodim (Select Max) in a 2021 tank mix can nix volunteer corn and prevent rootworm from infesting 2022 corn, he says.

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