The calendar used to play a significant role in David Hula’s decision on when he would head to the field and start planting corn. That’s not the case anymore.
“I’m not so hung up on the date now as I am on the temperature at which we’re putting seed in the ground,” says Hula, owner of Renwood Farms near Charles City, Va.
That doesn’t mean he pays no attention to the calendar, though. Sometime during the last week of April through the first week of May is usually the sweet spot to start planting corn, Hula says.
But that’s not always true. Experience has taught him that it’s more important to focus on the extended weather forecast than the date, making sure he has a soil temperature above 55°F at planting time and growing degree units (GDUs) that are accumulating quickly.
“Fifteen or so years ago, we used to talk about wanting to get 40 GDUs in a five-day forecast after planting,” he recalls. “Now, as we’re getting into these higher-yield environments, I want an even higher GDU accumulation in those first five days after planting.”
That kind of attention to detail has helped Hula achieve top honors in the National Corn Yield Contest 12 times over the years. His 623.8439 bu.-per-acre yield in 2023 marked the fifth time he set the record for U.S. corn yields.
The More GDUs, The Better For Emergence
While the required amount can vary somewhat by hybrid, a common range of GDUs needed for corn to emerge is between 100 to 150 GDUs, according to Ken Ferrie, Farm Journal field agronomist.
Ferrie says referencing GDUs offer growers a more reliable method to predict corn emergence as well as key development stages during the season than the use of calendar days.
“The amount of GDUs a specific corn hybrid requires to reach each development stage during the growing season remains constant from year to year,” he says. “However, the amount of time a specific hybrid needs to accumulate those heat units can vary considerably each year due to planting date, field conditions, soil temperature and weather conditions.”
Those factors, which can be highly variable, are why Hula focuses so much on having a good extended forecast at planting. “We want that corn to come up out of the ground fast,” he says. “In our best yielding years, that’s one of the things we’ve had.”
Hula defines fast as seeing the crop spike at between six and (not quite) seven days, emerging in a uniform, picket-fence stand across the field.
Scrutinizing management and agronomic details and tweaking them as Mother Nature dictates instead of just relying on a calendar date makes fast, uniform emergence achievable, he tells fellow corn yield champion and Total Acre business partner Randy Dowdy, who’s based near Valdosta, Ga.
Planting Practices Impact Corn Development
Something Dowdy and Hula say other corn growers could benefit from is paying more attention to planting depth and germination depth. Ideally, they end up being one and the same.
“I want my seed to be planted at 2”, and I want it to germinate at 2” and stay there,” Hula says. “I don’t want a scenario where all of a sudden we get some rain, and the soil is compressed, so now that seed germinates at 1.5”.”
Planting corn at a depth of 2” when soil moisture is adequate is ideal for nodal root development, according to Paul Yoder, Pioneer field agronomist. Nodal roots are vital for structural support and are responsible for most of the water and nutrients the plant needs. Five sets of nodal roots are optimal for maximizing potential.
The Mystery of Shifting Soils Explained
Dowdy tells Hula that corn growers are often puzzled by how their corn roots have developed when they check fields a month or so after planting. The growers are certain they planted their corn at 2”, but the evidence says otherwise.
“We’ll be digging some plants, and we’ll see a lot of brace roots above the ground,” Dowdy says. “That initially makes me wonder if the farmer had a wind event or some type of stress, because there’s a lot of issues with the root development.”
More often than not, Dowdy says the issue is the soil above the seed settled – either because of poor attention to detail while the farmer planted or from a significant rain event. If the ground settled, then the corn likely germinated and emerged at a soil depth shallower than desired.
“It often depends on what type of tillage you’re using, if you’re running trash sweeps, or a no-till coulter, and then what kind of closing system you have,” Hula explains. “A lot of times people don’t want to believe that, but it happens.”
Dowdy adds that it’s not just the conventional growers who experience the problem of the ground settling.
“It happens in all scenarios, whether in vertical till, strip-till or even in a stale seedbed,” Dowdy says. “Year to year, we just don’t know how much that ground is going to settle.”
A Pro Tip For Checking Planting and Germination Depth
Corn growers can simulate ground settling with a practice Dowdy and Hula use for that purpose: they smack the soil.
“Take your hand and use the bottom of your palm to hit the soil just above where you planted the seed. That’s going to simulate a rain event and give you a good indication of how that ground would or did settle, and what your emergence depth is,” Dowdy explains.
For growers in the process of planting corn, Hula encourages them to get off the tractor and check the quality of their planting practices.
“Check every corn row, not just one of them,” Hula advises. “Every row is an individual, so take time to check each one and make sure they’re all the same. Adjust as necessary for uniform planting.”
More Insights Available In Breaking Barriers Podcast
Dowdy and Hula are sharing their agronomic insights in their Breaking Barriers podcast to challenge growers to think differently to farm better and maximize profits.
In this week’s discussion, they address a variety of timely topics, including:
- reasons to plant three or four different populations of corn in a field
- how to use a flag test to evaluate emergence and development
- the value of setting yield goals to reach higher yield levels
- using tissue sampling in-season to add more yield
Watch the podcast at Farm Journal TV - Agriculture video on demand
For more insights on Hula and Dowdy’s planting progress and agronomic insights, check out their discussion with Chip Flory on Breaking Barriers - AgriTalk
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