Optimize Corn Emergence
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Modern planters and monitors, advanced hybrid genetics and seed treatments help achieve better corn emergence. However, mother nature and farmer impatience can be the most significant risk factors to corn emergence.
“Each spring, I get farmer calls about delayed or uneven emergence, missing plants or comments like the corn looks terrible,” says Dan Quinn, corn production agronomist at Purdue University. “Upon examination, the number one reason is planting too wet, and number two is planting too shallow into more variable moisture and temperature.”
Sidewall compaction caused by planter openers’ smearing wet soil creates a nightmare for the rest of the season. That’s why Quinn reminds growers to prioritize drier and warmer fields and check furrows soon after pulling into a new field.
“By opening up some furrows to check seed placement and sidewalls, it quickly becomes clear if it’s too wet or too shallow,” Quinn says. “If the corn is stressed out of the gate, it is not as tolerable to stresses the rest of the year, including diseases, insects, and lodging.”
Temperature and GDDs
Planting in 50-degree soils or lower leads to slow emergence, unless a warming trend is forecast, and Growing Degree Days (GDDs) are increasing. Crop residue coverage, seed depth and moisture can make these temperatures cooler and impact emergence timing.
Corn seedling emergence can take three weeks in 50- to 55-degree soils or 10 to 12 days in 60-degree soils with adequate soil moisture and seed-to-soil contact. Any delays can impact emergence and plant size variability, in addition to attacks from diseases and insects.
Use Growing Degree Days to ballpark your corn emergence, based on an air temperature formula. It can range from 90 to 120 GDDs for emergence, or 125 to 130 GDDs in the upper Midwest. “You want to see GDD accumulation fairly rapid after planting to get it out of the ground quickly,” Quinn says.
No-till fields or planting into cover crops with higher surface residue makes the soil more variable, so planters equipped with variable downforce and appropriate row cleaners help keep planting depth more consistent.
Planting Depth Critical
Photo caption: Proper planting is a key factor to optimize corn yields.
“It’s best to keep corn seed at a 2-inch depth for more consistent temperature and moisture,” Quinn says. “If moisture is lacking, you can plant at 2.5 to 3 inches deep, just be cautious of potential crusting issues that could delay emergence.”
Once corn plants have emerged, field scouting with a shovel helps diagnose issues, check stand counts and monitor weeds. “You can tell quickly by digging, as roots will indicate whether it is disease, insects, fertilizer or compaction issues,” he says.
Quinn worked with a farmer last spring, placing different colored flags by plants that emerged a few days later. When they examined those plants before harvest, the later emerging plants were small, spindly, with no ear—no different than a weed that competed for water, sunshine and nutrients.
“It’s a good method to estimate the number of plants lost per acre. Given this revised population, you can calculate a yield loss estimate,” Quinn says.
Weed Competition
Another yield-robbing factor in areas where corn plants fail is weeds that outcompete the crop. Certain weed species can be aggressive and interfere with corn crop emergence.
“There’s also a lot of research that shows young corn plants can sense weeds next to them based on light reflection,” Quinn says. “This event can trigger a stress response in corn, making it critical to maintain a good soil residual herbicide program and a timely post application during early corn growth stages.”
Top weed worries in corn have been consistent over the past decade, according to the Weed Science Society of America surveys. Waterhemp, Palmer Amaranth, morningglory, giant ragweed, common lambsquarters, Johnsongrass and kochia rein as the most difficult to control.
Herbicide resistance continues to be the common denominator among these winning weeds. Waterhemp, for example, has evolved to evade six different herbicide sites of action and achieve some metabolic resistance in several Corn Belt states.
For 2025, agronomists and weed scientists suggest doing everything possible field-by-field to keep these target weeds from going to seed. Changing and tracking herbicide modes of action used in every field during different crop rotations is a good start to eliminate repetition.
As weeds continue to win, consider trying diverse tactics like cover crops, targeted mechanical weed management, possible small grain or forage rotation, and even delayed soybean planting to improve control, for example, of late waterhemp emergence.
Visit these resources for more information:
- Corn Growing Degree Day tool
- Soil Temperature and Corn Emergence
- Requirements for Uniform Germination and Emergence of Corn
- Herbicide Resistance Management
- 2025 ISU Herbicide Guide: Corn & Soybean Production
Content provided by DTN/The Progressive Farmer
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