High-yielding hybrids are available in both round (above left) and flat (above right) seed corn, as the various sizes and shapes of kernels on the ear are genetically identical.
Baby your seed corn to help minimize damage
Every kernel of seed corn is wrapped in a thin protective coat, called the pericarp, which covers the seed like skin and provides its first line of defense against insects and disease. The pericarp also helps shield the seed from any rough handling during the planting and harvesting processes.
Round seed is particularly vulnerable to damage because the germ area is not as protected within the kernel as it is in flat seed. That’s not to say flat seed is better than round seed. High-yielding genetics are high-yielding regardless of their shape.
"Genetically, the various sizes and shapes of the kernels coming from an ear are identical," explains Bob Nielsen, a Purdue University Extension corn agronomist.
The differences in size and shape are due to the position of the kernel on the cob. Small rounds tend to come from the tip of the cob, large rounds tend to come from the butt of the cob and flats tend to come from the middle of the cob.
"Stress often affects tip kernels more severely because they are the last to be pollinated and are therefore the youngest kernels on the ear," Nielsen says. "Large rounds are difficult to handle without causing damage during the seed conditioning process because the embryo face of a large round is more exposed than it is on flats."
Mechanical damage during processing can be common for large round seed, says Farm Journal Field Agronomist Ken Ferrie.
Ferrie adds that round seeds from the top of the ear are more susceptible to insect damage in the field.
Nielsen encourages farmers to ask about seed testing results when making their annual seed corn purchases.
"Problems with seed quality aren’t always evident from the warm germination ratings on the seed tag," Nielsen says. "If you have questions about the quality of large or small rounds, ask your dealer for the cold germination ratings. If certain seed lots’ cold germination ratings appear suspect, consider planting them last to allow for maximum soil warming to encourage rapid germination."
Ferrie says that if you have a bag of seed with a high percentage of pericarp damage, don’t plant it because it’s more prone to go out of condition.
When it comes to handling lower thresholds of pericarp damage, Ferrie and Nielsen agree that seed lots with 3% damage or more should not be planted until the soil is above 50°F for 96 hours to reduce seed chilling issues.
"Don’t put starter fertilizer in the row when the pericarp damage is above 5%," Ferrie advises. "Seeds with that level of damage are more susceptible to salt burn from the starter. The resulting stand loss from the burn will negate the potential yield gain attributed to the starter."
Seed source. Know as much as you can about the seed you plant. Learn about the company’s quality standards and its quality assurance procedures.
"It doesn’t matter where the seed is sourced from as long as the seed quality is there," Ferrie adds.
How farmers calibrate their planter often has a greater impact on yield outcome than seed size and shape.
The most common seed size effects on yield relate to plantability issues. For example, plantability problems often occur if planters are not adjusted for the seed size that is being used. Excessive numbers of doubles (two seeds dropped at the same time) or skips can easily reduce grain yield by
3 bu. to 10 bu. per acre.
- Seed Guide 2011