By Claire Keyes
Progressive Farmer Contributing Editor
Mike Cerny is a bean counter. The southeast Wisconsin farmer used to plant soybeans at a rate of 180,000 seeds per acre in 15-inch rows. In 2013, he dropped his seeding rate to 165,000; in 2014, he trimmed it to 160,000 seeds per acre.
"Now I'm contemplating dropping a little more next year, as I have not seen any reduction in yield whatsoever. In fact, this year, I averaged 68.5 bushels per acre, my best yield ever," Cerny says. "With the improvements in soybean genetics and seed treatments, I'm finding that we can get by with planting a lot less seed," he says. Cerny raises soybeans, corn and wheat on 1,000 acres, near Sharon, Wis.
His experience aligns with results of a two-year University of Wisconsin search for the economically optimal seeding rates (EOSR) for soybeans. The research found that seeding rates can be lowered substantially by using a fungicide/insecticide seed treatment.
"We wanted to evaluate the trade-offs to maximize profitability and yield, and minimize the risk of planting too few seeds and reducing yield," says Shawn Conley, University of Wisconsin soybean and wheat agronomist.
The study looked at seeding rates of 40,000 to 140,000 and compared soybeans with no seed treatment with insecticide-only seed treatments and fungicide/insecticide seed treatments. It also factored in market prices of $9 per bushel and $12 per bushel. Top yield across the projects was 64 bpa.
"The research shows that at $9 beans, the economically optimal seeding rate is 111,000 to 112,000 per acre. With a fungicide/insecticide seed treatment, we can take that seed count down to about 94,000. This factors in the cost of seed, seed treatment and the resulting yield," Conley says.
In the research, Conley and his team found that a combination fungicide/insecticide seed treatment provided the lowest economic risk across a variety of environments, seeding rates (80,000 to 140,000) and grain sale prices ($9 per bushel and $12 per bushel), and allowed for a lower seed rate compared with no seed treatment or a fungicide-only seed treatment. They also found the EOSR for the fungicide/insecticide combo ranged from 94,000 to 101,000 seeds per acre, which was about 18% less seed than insecticide-only and untreated checks across grain prices of $9 per bushel and $12 per bushel.
"If growers want to plant more seed, we see a small, incremental yield gain, but it's just enough to cover the cost of the additional seed," Conley says.
He encourages growers to consider the expected grain sale price and the use of seed treatment when determining their economically optimal seeding rate. He offers these suggestions to pick the best varieties for reduced seeding rates:
-- Start with yield. "Look at many resources for performance data to identify consistent performers, including university trials and seed company data. Then, look at disease package and agronomic characteristics for those acres that make sense."
-- Select seed treatments. "Seed treatments are especially important as growers are planting earlier. Choosing a fungicide/insecticide combination provides the greatest protection and allows for the lowest seeding rates."
-- Consider maturity group. "The maturity group may be the final criteria you use to select between varieties, but it should not be your first consideration."
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