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Planting soybeans early may lead to yield gains

Hopes of high yields and extra income have spurred many farmers to plant soybeans earlier than ever.

“With any trend, the proof is in the pudding,” says Mark Worner, an Agoro Carbon Alliance agronomist. “I think most operators are seeing, when the stars align to get their beans in earlier, they’re getting a better return on investment with the yield on those acres.”

More capable equipment has opened the door for earlier planting. “From a grower standpoint, the capabilities have improved their ability to get across a lot more ground, a lot more quickly,” says Bruce Battles, a technical agronomy manager for Syngenta. “That extra capacity allows them to start thinking about [early planting] where historically they haven’t had that opportunity.”

The Science Behind Better Yield

Soybean maturity relies on photoperiods, meaning an earlier planting date will facilitate more vegetative growth before the summer equinox.

“As a general rule of thumb, once the daylight starts getting shorter, soybeans start thinking reproductive instead of vegetative,” Worner says. “If we can get our soybeans in earlier and have more vegetative growth by the 21st of June, we’re setting that plant up to have more nodes at its maturity. With more nodes comes more pods. More pods mean more beans and a higher yield.” 

Geography can also play a role in the correlation between planting dates and final yields. 

“Early planting means something different for different people and different geographies,” Battles says. “If you’re in southern Illinois, planting in the first half of April has really shown its value, but that doesn’t necessarily mean the same planting dates exist for central Iowa.”

29488_soybeanpods
Gil Gullickson

Benefits Beyond the Bank

A greater yield isn’t the only benefit to planting early. The resiliency of soybeans can allow farmers to better manage their time around planting. “If we plant beans into soils that are a touch wet or a touch cold, we have a better success rate for not having to come back and replant the crop than we do with corn,” Worner says. “From a time-management standpoint, it allows a grower the opportunity to start on some acres when the weather is not quite right for corn.” 

Increased early ground cover can also minimize headaches later in the season. 

“I think one of the bigger values of it that’s not talked about is getting good cover of the soil,” Battles says. “There’s a built-in weed control by getting an earlier canopy. By doing that, you’re not only holding weeds down, but you’re more efficiently harvesting sunlight.” 

The Summer Solstice
Soybeans shift resources from the vegetative stage toward reproductive ones after the longest day of the year. Forming more nodes by June 21 ultimately creates more yield potential.

Management Considerations

Several key management steps can help farmers make the most of early planted soybeans. Deeper planting depths can protect the seed from changes in soil temperature. 

“That soil profile temperature is going to be more consistent the deeper you go,” Worner says. “When thinking about emergence, we want that soybean to be at a depth where it’s not going through rapid cooling and heating cycles.” This can confuse soybean emergence and germination, he adds. 

Finding the right soil type and field conditions is essential when planting deeper. 

“If you’re trying that [planting deeper] in soils that are prone to crusting or hard emerging soils, it’s going to be more challenging to get an early planted bean crop up,” Worner says. “You have to be a little choosy and try to find some of your better acres where you don’t fight emergence problems.” 

Cool and wet soils can also lead to increased disease risk. 

“Anytime the soils get cooler and stay wet longer, you can get exposure to a lot of pathogens and slow down the plant in general,” Battles says. “The plant is less able to outgrow disease development on the roots or stems as a consequence.” 

A seed treatment can protect the plant early in the season. 

“One of the biggest things that I’d encourage people to do is use a soybean treated with an insecticide and a fungicide and really try not to cut corners on that,” Battles says. “You’re going to stress early-planted crops more than any other.”

Optimistic Outlook

Despite the risks, early planting of soybeans can show an exciting yield bump when conditions align. Most farmers can expect a yield increase of 3 to 4 bushels per acre when planting early but after April 11, says Mark Licht, an Iowa State University Extension agronomist 

“I’ve seen some very drastic improvements in yield where I went out and planted a few fields of soybeans first and then switched to corn before finishing soybeans,” Worner says. “Almost every time I’ve done that my early-planted soybeans have yielded higher than late-planted. To the grower that hasn’t tried it yet, give it a go and have confidence that it can work.”

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