Thin the Field

Soybeans Stands: How Low Can You Go?

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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You're better off spending money on more herbicide modes of action than dumping another 10,000 soybean seeds per acre, Wisconsin agronomist Shawn Conley says. (DTN photo by Pamela Smith)

ROCKVILLE, Md. (DTN) -- There's never been a better time to lower your soybean seeding rate.

Backed by genetic advances and modern seed treatments and facing dismal soybean prices, Virginia farmer Stephen Ellis has been steadily thinning his stands for years.

"We have never gotten low enough that it harmed us on yield," he told DTN. "That's why I keep going lower."

Currently, Ellis is averaging 120,000 seeds per acre on his early planted soybeans on his family's row crop operation near Tappahannock, Virginia. He has experimental plots ranging from 240,000 to 30,000 seeds per acre.

Science is on his side, said University of Wisconsin Small Grains Specialist Shawn Conley.

"Soybean breeders have effectively cut the yield penalty for a thin stand in half," he told DTN.

Add protective seed treatments and early planting efforts to the mix, and growers are perfectly positioned to push soybean yield potential higher than ever, with fewer seeds than ever, Conley said.


The soybean is already extremely adaptable, Conley noted. "The plants have an innate ability to branch," he said. This allows plants to fill in gaps in the canopy and regain yield potential in thin stands.

Enter soybean breeders.

Ellis is accustomed to planting cutting-edge genetic packages each year, because he grows many of his beans for a company's seed production.

Those beans are miles ahead of the ones growers planted just 20 or 30 years ago, Conley said.

A few years ago, the Wisconsin researcher participated in a soybean study with germplasm dating from 1928 to 2012.

"In low-population environments, the modern soybean plants were able to put three times as much as yield on those branches than they used to be," he said.


Although he favors the 120,000-seed range, Ellis believes many growers in his region could drop as low as 90,000 without much yield penalty.

A recent economic study from Conley showed that growers were most likely to make a profit in the current market with soybean rates ranging from 103,000 to 112,000 seeds per acre.

The catch? Seed treatments are key.

"If you plant that low, you've got to have everything on that seed, so you don't you lose any of that stand," Ellis said.

For most soybean growers these days, that's a given.

Ten years ago, as few as 8% of soybeans went into the ground with any products on the seed. Today, that number is pushing 80%, Conley said.

Ellis's soybeans come to him fully packed with an insecticide, fungicide, inoculant and growth regulator.


Early planting is the most reliable way to push soybean yields higher, Conley said.

Fungicide seed treatments have permitted growers to safely push their soybean plant dates into mid-to-late April.

Ellis actually finished planting his early soybeans on April 19, a day before he wrapped up corn planting.

He credits that early planting date with his ability to maximize yield on thinner stands. Later-planted soybeans require heavier stands.

"We start at 120,000 and then add 20,000 per week" starting around mid-May, Ellis said. By the time his double-cropped beans go into the ground in mid-June, he's planting 180,000 to 200,000 seeds per acre.

Narrow rows are key for better managing thin stands, Conley said.

Ellis drills 15-inch rows. "It just makes a bushier plant that sets more nodes -- more places to set pods," he said.

Narrow rows can also save growers on weed control, as canopies close faster, Conley added.


Planting heavy soybean populations used to be a cheap insurance option.

With pricey biotech seed, default-added seed treatments and low commodity prices, that mindset no longer makes sense, Conley said.

He contends that farmers' thinly stretched budgets would be better spent elsewhere.

"You're much better off paying for another mode of action against waterhemp and Palmer than paying for another 20,000 seeds per acre," he said.

See Conley's economic study on soybean seeding rates here:….

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Emily Unglesbee