When Less Is More

July 27, 2012 10:45 PM
When Less Is More

Reduced soybean seeding rates can boost profit

Less soybean seed at planting can add up to more bushels in the bin at harvest. That equation sounds fictional, but agronomic research and real-farm experience have proven it as fact to Ben Moore.
To date, the northeast Indiana farmer has cut his soybean seeding rate by as much as 10%, depending on the field. He says overall yield results are at least as good as before, if not better.
"We’ve learned that we were putting more seed on than what we needed to," explains Moore, who farms 2,000 acres of dryland soybeans on heavy clay soils with his uncle, Steve, near
Woodburn, Ind. In addition to soybeans, the Moores grow corn and wheat and own a wean-to-finish hog operation.

Too much at stake. The Moores began tinkering with their soybean seeding rate three years ago.
"The increase in soybean prices got us looking at this," Ben says. "You can spend a lot more time and effort on soybeans when the price is $13 a bushel versus $6."
Along with the surge in prices, Moore says, the simultaneous increase in soybean seed costs also contributed to his decision to fine-tune his planting rate.
"Managing inputs effectively is just as important to profitability as price," he says.
This year, Moore planted between 150,000 and 165,000 seeds per acre in 20" rows. His goal was to achieve a final stand count of 127,500 to 140,000 plants per acre. University research indicates he might still have room to reduce seeding rates and achieve an optimum plant stand.
"Our small plot research has demonstrated that harvest stands near 100,000 to 120,000 plants per acre optimize yield," says Shaun Casteel, a Purdue University Extension specialist. "In other words, soybean yields do not effectively increase with plant stands above 120,000 plants at harvest."
Just 100,000 uniform soybean plants per acre at harvest is often enough to maximize economic return, adds Palle Pedersen, seed care technology manager for Syngenta.
"For maximum yield, the stand count at harvest is most important," he says.
In general, Moore says, his fields with higher soil organic matter and fertility are able to handle a higher seeding rate range. Fields with less natural fertility, what Moore calls his "tough ground," are planted with seeding rates in the lower range.
Yields at harvesttime correspond accordingly.
"Depending on the field, we’ll see yields average from a low of 30 bu. per acre up to 80 bu. per acre," Moore says.

Establish a review process. During spring planting, Moore plants replicated strips of soybeans in each field. Yield maps are then created and eval-uated during downtime the following winter.
"We can mark those zones where we changed rates to see if there’s a yield response in those areas," Moore says.
In the course of comparing and contrasting yield results between each field and its respective strip test, Moore also takes into consideration the inputs used, soil quality and weather factors.
Now in the third year of the process, Moore says he is beginning to see some trends, which are helping him fine-tune seeding rates field-by-field. That goal is made easier to achieve with a variable-rate drive on his soybean planter, which enables him
to increase or reduce seeding rates on the fly.

Recipe for success. Casteel says that as farmers determine their seeding rate, they should take into consideration that roughly only 85% to 95% of the viable seeds planted will emerge and establish a stand. It all depends on the accuracy of the seed’s placement, residue issues, weather and other field conditions.
Upon seed emergence, farmers can then benefit from evaluating how many seeds actually produced viable soybean plants, says Kraig Roozeboom, Extension soybean specialist with Kansas State University.
"Soybeans are notoriously inconsistent in their ability to germinate and emerge to form a viable stand," Roozeboom explains.
"Take appropriate steps with seed handling, soil moisture and planter adjustment to maximize stand establishment," he says.
Don’t overlook the soybean variety selection process, adds Greg Roth, Extension soybean agronomist at Pennsylvania State University.
"Of all the inputs we evaluate, some of the largest yield differences we see are due to varieties," Roth says.
On-farm testing is still the best way to determine which varieties will yield best for a specific grower, he adds.

Protect the investment. Moore says he likes to plant bushy soybean varieties with strong offensive traits.
"We can help [the crop] on the defense side with our pest management, scouting, fungicide and fertilizer applications," he says.
With the help of his independent agronomist and his seed salesman in the variety selection process, Moore is still evaluating how different soybean maturities play into his quest for optimum yields. He typically plants soybeans that have a maturity range of 3.0 to 3.8.
"If we can plant early, we’ll plant a full-season soybean. If not, we’ll go into the field with something earlier. We’re still playing with maturity," he says.

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