Many seedsmen and farmers alike say they’re not aware of many people backing off on corn seeding rates for 2016 just to save money. Yet some agronomists say the opportunity is there. They point to data that indicate that you may not take that big of a yield hit for doing so.

Tom Stein, a certified crop adviser (CCA) and manager of Ceres Solutions branches in Boswell and Templeton, Ind., was recently asked to address one farmer’s situation.

OPTIMUM YIELD OR PROFIT? Several agronomists say there’s a difference between how thick corn should be to reach top yield, and how thick it can be to reap the most return per acre.

I’ve been planting 33,000 seeds per acre. After reading articles about a fairly flat yield curve for population in this range, I may back off to 29,000 as a seeding rate to save money. Is that reasonable? I have average to good soils. Am I taking more risk by cutting back to that level?

Here is Stein’s response. Remember, he’s just one agronomist and this is his opinion.

“Seeding rates for corn have increased readily over the past several years in an attempt to take advantage of genetic improvements in stress tolerance of newer corn hybrids to achieve maximum yield potential. The desire to reduce your seeding rate from 33,000 seeds per acre to 29,000 seeds per acre is not unreasonable, and there is research to support that decision.”

If growing conditions are good and you have the soil to support it, higher plant populations offer the potential for the best yields, he says. However, the optimum agronomic seeding rate is different than the optimum economic seeding rate.

Optimum economic seeding rate

The optimum agronomic seeding rate results in maximum yield regardless of cost, Stein says. The optimum economic seeding rate is the seeding rate that generates the most income when yield, seed cost and grain price are factored in.

Stein says that in an attempt to evaluate yield response to plant population, Purdue University researchers — primarily Bob Nielsen and Jim Camberato — have conducted 67 field-scale trials with growers since 2008. Those findings show that the maximum agronomic seeding rate for corn under normal growing conditions was 34,000 seeds per acre, which resulted in a final population of 32,000 plants per acre.

“However, the optimum economic seeding rate for $3.50-per-bushel corn and a seed cost of $275 per 80,000 kernels, was 28,800 seeds per acre,” Stein observes. “That’s right within the range of your plan.”

Another believer

Here’s what another agronomist says. Greg Kneubuhler, also a CCA, owns G & K Concepts near Harlan, Ind., and works with farmers in northeast Indiana and northwest Ohio.

“We’ve done thousands of acres of yield prescriptions,” Kneubuhler begins. His firm specializes in conducting tests and working with farmers who do a fair amount of on-farm testing.

“Our testing strips within our prescriptions have proven to us that lower seeding rates will prevail most of the time,” he continues. “The seed industry tends to push us to higher rates. However, we’ve found that isn’t necessarily the case.”

Kneubuhler says that based on his observations, if you have average to good soils, most hybrids will tend to flex and handle lower seeding rates. “Study the characteristics of hybrids you’re planting,” he says.

One thing you want to know is whether the hybrid sets a determinate or flex ear. There are still a considerable number of hybrids with determinate ears, with fixed ear size, on the market.

Talk to your seedsman, Kneubuhler suggests. You want to make sure you aren’t cutting seeding rates too fine on a determinate hybrid. That could leave yield on the table.

“Most of our economic response curves on population tend to break around 32 to 33,000 plants,” he says.

Note that’s considerably higher than where the curve breaks based on the study Stein reported on earlier.

“Cutting back to 29,000 across the board may be a little aggressive, unless we end up with a late planting season,” he adds.

Another view

Jesse Grogan, an agronomist with LG Seeds, based in Lafayette, Ind., points toward the risk side of the equation for cutting back seeding rate. “Seeding rate is dependent on hybrid background and yield potential with soils and applied management,” he begins. “Making changes that are more than 1,500 to 2,000 seeds per acre from your average in one year without a good agronomic reason is risky to me.”

Grogan outlines four things he would do before changing seeding rate settings from a year ago.

Consult your seed rep. Ask him or her for seeding rate recommendations by hybrid.

Look for articles or other sources of information that allow you to gauge where your seeding rates are compared to other farms.

Reflect on how each of your fields responds to management practices. Nobody knows them better than you do.

Test or evaluate changes on your farm before applying these changes to a majority of your acres.

Seeding rate vs. plant population - know the difference

Any discussion about corn seeding rates should be prefaced by making sure you know
if you’re talking about seeds per acre or plants per acre.

Bob Nielsen, Purdue University Extension corn specialist, has made this point repeatedly in talks over
the last couple of years.

Research by Nielsen and Jim Camberato points to an agronomic optimum population of 32,000 plants per acre, as noted earlier. Nielsen prefers to make that point, and let people figure out what seeding rate they should select to achieve that goal.

Why? Because some people are more successful at achieving good stand establishment than others. Put another way, make up your own mind on how much cushion on seeding rate you need to obtain the final plant population you want at harvest.

Nielsen has emphasized repeatedly that it is final plant population at harvest that counts.

Here are 10 factors that could affect how well you convert seeding rate into final population:

1. Planter maintenance before the season begins

2. Calibration of planter meters or vacuum units with actual seed you will plant

3. Soil condition at planting — is soil too wet?

4. Ability of closing wheels to close the seed slot

5. Uniform placement of each seed at the same depth

6. If seeding disks on planter are worn and not working properly

7. If you are planting into no-till or conservation tillage fields, where residue could interfere with planting

8. Germination percentage of the seed — check the seed tag

9. Early-season vigor of the hybrid — ask your seedsman

10. Selection of planting date based on adequate soil temperature

- Decision Time: Production is independently produced by Penton Agriculture and brought to you through the support of Case IH. For more information, visit farmprogress.com/decisiontime.