Alabama Corn: Factors to Consider When Selecting Seed

Corn seed bags for planting. ©Debra L Ferguson Stock Photography

Most growers have enjoyed the holidays and are making corn decisions for 2018’s crop. Many farmers may have already received a visit from their corn seed supplier wanting them to book their seed early.

There are many factors involved in selecting a variety including standability (especially important for corn planted at higher populations); disease tolerance; relative maturity; suitability for dry land production (drought tolerance); and transgenic resistance to insects and herbicides, but for most farmers the main component in choosing a variety is yield.

Personal experience under growers’ soil types and production practices is the best way to determine yield potential but most growers don’t have yield trials on their farms. I am attaching the results of our on-farm corn variety trials in north Alabama.

Another great source when looking at the yield potential of a variety is Alabama’s results in the National Corn Growers Association Yield Contest. I am attaching the state-by-state results of the 2017 National Corn Growers Association Yield Contest.

Growers should also request the same shapes (flats or rounds) and sizes (small, medium or large) when ordering seed. Randy Dowdy, the first grower in the world to produce 500+ bushels of corn per acre, notes, “What we don’t want is a variation in seed shape and size. I don’t feel they can imbibe water and emerge at the same time unless they are the same shape and size.”

Dowdy doesn’t have a preference on flats or rounds but advises growers to plant what their planter would do the best job planting.

Dowdy says, “The key to high yields is getting a uniform stand. I want all my plants to come up within ten growing degree units of each other.”

Growing Degree Days (GDDs) and Growing Degree Units (GDUs) refer to the same calculation based on air temperature. The equation for corn is: GDD or GDU = (Daily Maximum Air Temperature + Daily Minimum Temperature)/2 minus 50.

When the maximum air temperature is greater than 86 degrees F, the value is set at 86 degrees in the equation as the growth rate of corn does not increase beyond 86 degrees. When the minimum air temperature is less than 50 degrees, the value is set at 50 in the equation.

The sum of daily GDUs or cumulative GDUs for corn emergence is approximately 90 to 120. Ten GDUs at planting in north Alabama is usually around 12 hours.

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