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How to Better Bean Yields

Grab a thermos full of coffee. Don your long johns. Cover your head with a stocking cap. Then, go plant soybeans. 

That’s because early planting is a key factor soybean farmers can use to boost soybean yields. 

“By pushing planting dates earlier, we can influence when the first flowers appear prior to the summer solstice (June 21),” says Josh Miller, BASF technical marketing manager for plant health. “That enables soybeans to capture the most sunlight possible during the critical reproductive stages.”

“Early planting means more vegetative growth,” adds Marc Hoobler, BASF soybean agronomy lead. “This means more nodes per plant, which means more pods per node.”

A 2018 trial at BASF’s research farm at Seymour, Illinois, showed that a 12-day delay (from April 26 to May 8) clipped yields by 7 bushels per acre. At an $8.50-per-bushel price, that’s a $59.50-per-acre loss incurred by nothing more than delayed planting.

University of Nebraska scientists found a similar pattern in a 2015 trial comparing irrigated 2.1 and 3.0 maturity group soybean varieties planted at 10-day intervals from April 23 through June 19. Soybeans planted early yielded the most, with a yield penalty of 1⁄8 to 1⁄4 bushels per acre daily occurring after the early date for both maturity groups. 

So Why Don’t More Farmers Do It?

Remember last spring’s soaking rainfall that plagued farmers in many areas? It’s hard to think about seeding soybeans when bullheads instead of planters roll down flooded fields. 

“If you have wet weather, you can’t get into the field early to plant and maximize this part of the puzzle,” says Brian Buck, a Pioneer field agronomist. 

Then there’s the corn component. “Most growers are always going to plant corn first,” says Josh Shofner, a Pioneer field agronomist. 

There’s good reason for that. Early planting also stokes corn yields. Early planting also helps ensure that corn matures and dries down on time. This minimizes drying bills, particularly for more northern farmers who start out with a shorter growing season than those farther south. 

If soils are fit to work, though, economic advantages exist for planting both crops early, says Shofner. Even in good springs, Midwestern corn planting often doesn’t wrap up until May 10. 

 “You have to look back at how many acres a bean planter could cover if it’s out there on April 20 compared to the middle of May,” says Shofner.

Farmers who wait to plant soybeans after corn lose yield potential, he adds.  

Provided farmers have another tractor and operator, simultaneously planting corn and soybeans is not as far-fetched as you may think, says Buck. Since corn seed is much more sensitive to spacing and depth than soybean seed, it makes sense to have a high-tech planter for corn, he adds.

”A basic row unit planter will do a good enough job for soybeans and be a cheaper option,” he says.

Other Steps

arly planting, though, is just one step of many on the road to better soybean yields. Here are six other steps.

1. Variety Selection.

“Address factors that are limiting yield in a field,” says Hoobler. For example, if soybean cyst nematode (SCN) is a problem in a field, select a high-yielding variety with SCN resistance.

There’s always potential for defensive traits that combat multiple maladies – such as SCN and iron chlorosis – to curb a variety’s yield potential. However, it’s not always a given that yield potential will be curtailed, he says. “You have to evaluate each variety toward producing in the environment you have,” says Hoobler.

2. Optimal Seeding Rates.

There’s good news here on the cost front. Optimal soybean seeding rates have dropped. “I remember that some farmers with drills used to plant close to 200,000 seeds per acre,” says Buck. 

Not now. “If you are in the 100,000- to 120,000-plants-per-acre (ppa) range (at harvest), you are fine,” says Shaun Casteel, Purdue University Extension agronomist.

3. Seed Treatments.

One reason seeding rates have been dropping is because seed treatments deter fungal diseases like Pythium, Fusarium, and Rhizoctonia. They’re also needed to help soybeans withstand the rigors of early planting. 

“In Minnesota where there are a lot of cool, wet spring soils, they’re an important part of soybean production,” says Shofner. 

They’re also a way to combat sudden death syndrome (SDS). Although symptoms often show up in August, infections actually start at plant emergence. Ilevo is a seed treatment that farmers can use to manage SDS, he says. Another SDS seed treatment, Saltro from Syngenta, will be available for farmers to use in 2020.

“SDS can be a big yield robber down the stretch that you have to protect against up front,” says Shofner. 

4. Adequate Fertility.

The good news is, soybeans take care of the nitrogen (N) component of a fertility plan by fixing their own. Not so with phosphorus (P) and potassium (K). Soybean farmers cannot rely on P and K applied on corn the previous year.

“When you push for 100-bushel-per-acre yields, plant uptake of those two nutrients can almost double,” says Shofner. “High-yielding soybeans correlate to (higher) phosphorus and potassium levels.”

Ditto for sulfur (S). Applications of this nutrient used to be beneficial on just sandy soils. No more. Antipollution laws that have stripped the atmosphere of S also have translated to the need for supplemental S applications, says Shofner.

5. Disease Control.

Frogeye leaf spot has moved northward and has infested a number of fields in areas like central Iowa. Unfortunately, frogeye leaf spot that resists strobilurin fungicides is also surfacing. 

Many fungicides contain both strobilurin and triazole active ingredients, says Dean Grossnickle, a Syngenta agronomic service representative.

“If you have strobilurin-resistant frogeye, the triazole will help, but as far as giving preventive treatment, the strobilurin (component) will not do it,” he says. One option is to apply a fungicide that contains multiple active ingredients, including one with SDHI chemistry, he says. 

6. Weed Control.

A preemergence residual herbicide is vital with soybeans, says Grossnickle. 

That’s easier said than done in a soggy spring. Still, Grossnickle advises farmers not to get their planters ahead of their sprayers. 

“Plant a field, spray a field,” he says. 

If soybeans are planted and three weeks of rainy weather follow with no preemergence residual herbicide down, it places excessive pressure on postemergence herbicides in herbicide-tolerant systems like glyphosate, glufosinate, 2,4-D, or dicamba to control weeds. 

“When there is too much pressure put on post products, you will find that unique weed that resists those programs,” he says.

What's Eating My Beans?

There was good news and bad soybean insect news in 2019.

The good news is, overall, soybean aphid infestations were down. The bad news is, a relatively new pest – the thistle caterpillar – infested many soybean fields this past growing season. 

“They were the biggest buzz of the year,” says Josh Shofner, a Pioneer field agronomist. “They fed on a lot of soybeans.”

The thistle caterpillar is aptly named due to its spiny back. It’s better known in its adult stage: the painted lady butterfly. Thistle caterpillars have two larval stages annually. Weather patterns likely fueled this year’s infestation, says Shofner.

“They can do quite a bit of vegetative damage, especially in the last couple of instar stages,” points out Brian Buck, a Pioneer field agronomist. The good news is, they vacate soybean fields once they reach about 1¼ inches in length.

An insecticide is recommended when 30% leaf defoliation occurs prior to the R1 (beginning bloom) stage, says Shofner. 

“If you don’t have a ton of pressure and they’re in the late instar stages, treatment isn’t recommended, because they’ll vacate the field at some point,” he says.

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