Revised Recommendations for Soybean Plant Population


As planters start to roll in the soybean fields, producers are grateful to learn that studies are showing a reduced soybean plant population doesn’t affect yield.  NC State Extension Soybean Specialist Dr. Jim Dunphy:

“Soybean populations have come down in the last 10 to 15 years, and understandably so.  As price of seed has gone up, interest in reducing seeding rates has increased, and that’s understandable.

“And with soybeans we’ve been able to reduce populations, in many cases, without affecting yield.  We don’t have to have as many soybean plants per acre out there as we originally thought.

“The people that taught us were originally coming from how many plants per acre could they tolerate.  Because it was a weed control tool…try to crowd the weeds out, and seed was very cheap.”

And now, a bag of soybean seed isn’t cheap.  So, any savings help increase the bottom line explains Dunphy:

“No, it isn’t.  And it’s understandably generated a lot of interest.  Seed is a much larger percentage of our cost of production, than it used to be, and that’s understandable.  We’ve got traits in our seed today that we didn’t have 20 years ago, or 30 years ago, and most of our farmers have decided that those traits are worth some extra money.”

Dunphy explains that population depends on planting dates:

“Depends on the planting date.  I need enough time to get the plants big enough to get the job done.  And if they’re not going to get big enough, I can help offset that a little bit, with having a few more plants out there.

“So, in May, our data would say we need about 75,000 plants per acre out there to maintain our maximum yield.  That’s lower than what most of our farmers would have guessed.  But, that’s kind of our minimum.

“In June, it’s more like 85-90,000 that we like to have, and in July 100,000 is kind of the minimum population that will still maintain maximum yield.”

Dunphy compares today’s seeding recommendations with previous years:

“Depends on how far back you go.  I grew up with a bushel to the acre, and knew of a lot of farmers that talked about a bushel and a peck per acre.  so, that’s 180,000 seeds per acre, give or take a little, depending on seed size.  Now, we’re talking, many cases…well, now a bag of seed that used to be 180,000 is now about 140,000 seeds per acre in a bag.  It’s kind of a norm, a bag of seed per acre.   But, that’s a reduction of probably 40,000 seeds per acre.

“I know about how many plants I want to end up, we don’t all agree, or won’t all agree, and I don’t know that we should, on how many extra seeds do we need to plant to make sure that I end up with at least that many plants per acre.” 

NC State Extension Soybean Specialist Dr. Jim Dunphy.

A native of the Texas Panhandle, Rhonda was born and raised on a cotton farm where she saw cotton farming evolve from ditch irrigation to center pivot irrigation and harvest trailers to modules. After graduating from Texas Tech University, she got her start in radio with KGNC News Talk 710 in Amarillo, Texas.