A father and son argued about tearing up a soybean stand. The population at the V2 stage averaged 80,000 plants per acre in 30-inch rows. Dad wanted to tear up the stand. His son wanted to leave it. In a rare turn of events, the son won. They left the stand. It was a good year for soybeans, and the field yielded 60 bushels per acre.

That was more than 30 years ago. Was it a fluke? Would a stand that thin yield below average in most years? Not likely, says Shaun Casteel. The Purdue University Extension soybean specialist doesn’t believe that situation was a fluke.

In fact, he points to data going back decades that indicates that if the stand is uniform and weeds aren’t an issue, 80,000 plants per acre, or maybe even less, can yield as well as 160,000 plants per acre.

Management tip
“It’s one of the management factors that many growers should re-examine heading into 2017,” Casteel says. “There are still many producers planting at a much higher rate than necessary.

“Soybeans are very forgiving, and can compensate for various conditions by forming more branches and pods on existing plants,” he explains.

Some bankers have already made it clear that they expect customers to figure out how to cut crop budgets for 2017. Purdue ag economists have produced 2017 crop budgets showing that while soybeans are more favorable economically than corn in many cases, there is still red ink even on soybean budgets when all costs are included.

Casteel says 100,000 to 120,000 plants per acre is probably a good goal for many producers. How low could stands go and still not affect yield potential?

“They definitely could go lower,” he says. “I would feel comfortable at 100,000 plants per acre. However, 100,000 to 120,000 plants per acre is probably a safer range for people who have been planting at higher rates. Even at 100,000 to 120,000 plants per acre, there is a safety factor built in.”

Cost factor
So just how much could you save on soybean seed cost without sacrificing yield potential? That depends upon your current seeding rate, but it could be substantial, Casteel says.

Casteel developed a chart (below) that indicates possible dollar savings per acre based on seeding rate, expected plant population and price per unit of seed.

Suppose you’ve been planting at 175,000 seeds per acre and drop to 125,000 seeds per acre at 90% germination, assuming 2,800 seeds per pound. You can expect about 113,000 plants per acre. Savings for making the switch would be $14, $18, $21 and $24 per acre for $40, $50, $60 and $70 per unit of seed, respectively.

Even if you only cut your current rate by 25,000 seeds per acre, you could still save about $10 per acre, depending upon seed costs.