Suppose you want to wind up at 32,000 plants per acre. You've found that on your soils that seems to be an ideal plant population to deliver the yield punch that you seek. Where do you set the seeding rate to achieve that final stand?
Related: Seed cost could impact seeding rate
Do you set it at 32,000? Bob Nielsen, Purdue University Extension corn specialist, says that's likely to leave you short of your goal at harvest time. You need to allow for some loss of emerged plants due to germination and emergence issues.
Seeding rate matters: Whether or not you reach your desired population goal at harvest depends on where you set the seeding rate when you plant.
After all, if germination is 95% on the tag, based on germination tests to determine that number, the best you should be hoping for in that case would be 30, 400 plants per acre. A 95% germination means 1,600 seeds won't germinate.
Some hybrids and lots of seed may do better than that, especially after years which favored growth and development of quality seed. However, if you factor in emergence issues, it's not unreasonable to expect a 5% difference between seeding rate and emergence, he notes.
When Nielsen analyzes how well a planter performed once the crop is up, he counts the distance between plants in inches down the row, repeats it at several locations, and computes a standard deviation.
If the planter was perfect and every seed came up, the standard deviation would be zero, he says. But planters aren't 100% perfect and every seed won't come up, he says. So he recommends a standard deviation of 2.0 as a good goal to shoot for if you're after evenly spaced stands that won't detract from yield.
So where does that leave you on setting the planting rate for your planter this spring? Factor in that several agronomists, including Brian Denning with Stewart Seeds, expect seed size to be somewhat smaller than normal, requiring adjustments in planters to hit the desired target.
"To hit the ideal of 32,000 plants per acre, farmers should plan on putting down 32,500 to 34,300 seeds per acre," Nielsen says.