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How to Better Your Bean Yields

It’s easy for farmers to get dreamy eyes and smile when they read about stratospheric 160- or 170-bushel-per-acre world record soybean yields. Unfortunately, that’s what they are on most soils – dreams. 

“Those are big, big yields – double or triple most yields,” says Ryan Van Roekel, a DuPont Pioneer field agronomist in Iowa. Those yields are rare and are often unrealistic. There are some fields that will never have the potential to yield 100 bushels per acre,” he says. 

Still, don’t give up. A field that normally yields 40 bushels per acre might yield 60 bushels with just the right touch. Ditto for a field that often yields 70 bushels per acre. It could be tweaked to go 100 with the right strategies and weather. Here are some steps from Van Roekel for how to do it.

look at pods

“The one thing I have noticed with 100-bushel soybeans is that they have more pods than a normal crop,” says Van Roekel. Prolific pods are fueled by light quality and quantity, which peaks on June 21, the longest day of the year. “Ideally, you want soybeans flowering by this date,” he says. 

Early planting is the way to do it. “Early planting not only intercepts more light, but also stretches out the reproductive period,” says Van Roekel. This spurs more pods and, ultimately, higher yields. 

Planting full-season varieties can boost early-planting benefits. “Full-season soybeans have more potential to stretch reproductive and vegetative periods,” he says. 

A 2011-2012 DuPont Pioneer study across 37 Illinois and Indiana locations compared full- and early-season varieties planted in mid-April to early May against late-May plantings.

In the earlier plantings, full-maturity soybean yields bested those of earlier maturing ones by 7.2 bushels per acre. The yield edge wasn’t as wide in the late plantings, though. In late May, full-season varieties outyielded earlier maturing ones by 2.7 bushels per acre.

“When you plant a full-season bean late, it shortens up the reproductive period,” says Van Roekel. “Even the best growing conditions can’t make up for lack of early planting,” he says. 

Planting Dates and Row Width in Soybeans

Drawbacks

Early planting isn’t always so rosy. A soybean’s growing point is above ground, exposing it to frost. Early frosts are especially a concern in northern states. Fortunately, killing frosts in May in areas like central Iowa are rare, says Van Roekel. 

Cold and wet soils are more common. “Every year, farmers will tell me they’re nervous about planting soybeans early,” says Van Roekel. “Soybeans are really resilient to cold and wet conditions. Early-planted beans might sit in the ground two to three weeks when it’s cold and wet, but they will come up pretty well.” 

They need help, though. 

“Soybeans in cold and wet soils are at a high risk for soilborne fungi,” says Van Roekel. This includes sudden death syndrome (SDS), a fungal malady in which late-season damage is rooted in spring infections. 

Meanwhile, bean leaf beetles will go to the first-emerged fields in an area. Thus, an insecticide/fungicide seed treatment is often recommended for early-planted soybeans, says Van Roekel. 

Variety selection can help fend off such stressors. “Finding a variety with high yield potential is important, but you also need to consider defensive traits. In my area (central Iowa), SDS is a huge factor. White mold can be another factor in more northern areas.”

If you don’t need defensive characteristics, though, aim for yield potential. Defensive characteristics can chip away at yield potential, says Van Roekel. 

Weed control also is key, and several herbicide-tolerant systems are available for farmers. “We sometimes see yield differences among maturities, where one herbicide-tolerant technology might be strong in earlier maturities and another one might be stronger in late maturities,” says Scott Beck, Beck’s Hybrids president. “As a whole, the platforms are comparable. We see parity among yields.”

Good drainage also helps soybeans get off to a good start. “With no (water) ponding stress, roots are able to breathe,” says Van Roekel. 

You also need to plant early-planted soybeans thicker. 

“It is not uncommon to lose 10,000 to 20,000 plants per acre in a normal spring,” he says. “A tough spring can knock off 30,000 plants. So you want to plant thick enough to have a final harvest stand of 120,000 plants per acre.”

Planting soybeans early often coincides with prime corn planting time. Planting them simultaneously requires another planter and operator. 

The good news is that a second planter or drill for soybeans doesn’t have to be fancy, says Van Roekel. Unlike corn, soybeans haven’t been proven to respond to uniform spacing. Minor gaps or doubles aren’t critical either. “Beans have a lot of room to flex, he says.

Triple Digit Yields in Soybeans

narrowing rows

Narrowing rows can help soybeans glean more sunlight. 

“Soybeans planted at a rate of 150,000 plants (per acre) in 15-inch rows intercept nearly 100% of sunlight,” says Van Roekel. “In 30-inch rows, the 150,000 plants in 30-inch rows intercept just half of the light, with the other half hitting the soil. Thus, each plant in 15-inch rows receive more sunlight, which equals more photosynthesis and more yield potential.” Narrowing rows from 30 to 15 inches has consistently boosted soybeans 2 bushels per acre in University of Illinois trials. Still, narrow rows can sink a soybean field with a white mold history.

Wide rows help circulate more air to curb white mold. One compromise may be 20-inch rows, Van Roekel says. 

hidden hunger

Soybeans typically require fewer inputs than corn. That’s not true in all cases, though.

“Soybeans take lots of potassium (K),” says Van Roekel. “There’s a hidden hunger where you may not see a deficiency, but it will surface in tissue tests. An 80-bushel crop can take up to 250 pounds per acre of K20.”

Soybeans also consume lots of N, at a 5-pound-per-bushel rate. More good news: Soybeans fix their own N. 

“Adding nitrogen to soybeans can be self-defeating because it interferes with nodulation,” says Van Roekel. “There is no consistent way to profitably add N to soybeans, especially with high organic levels. It can sometimes decrease yield rather than increase it.”

Not so with sulfur. “We are getting to the point in Iowa where sulfur should be standard in a fertility program,” he says. 

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