Corn: Insights on Planting and Early Frost Damage

Above normal spring temperatures coupled with drier weather have hastened the 2015 spring planting season in South Dakota (SD). The USDA-NASS crop progress report released on April 20th showed that the corn acreage planted this year more than doubles the five-year average, and is five times greater than the last year’s alone. The corn planting window in SD historically ranges from late April to early June (South to North) depending on field and weather conditions. Corn is a warm season crop and as a general rule, soil temperature should be at least 50° F for seeds to germinate. Soil temperature above 50° F will rapidly facilitate germination and emergence.

Hybrid Selection
Selecting a hybrid with strong adaptability to the growing region is the first thing to consider. Growing hybrids with proper relative maturity allows the crop to take full advantage of the local weather conditions (or heat units), mature before the first killing fall frost, and also yield to its full potential.

The annual variety trial results gathered by Crop Performance Testing at South Dakota State University is an effective tool to select hybrids for a particular select growing region.

Seeding Rate and Depth
Seeding rate largely depends on germination, moisture, soil nutrient availability, and soil management. The optimal corn plant population ranges from 22000 to 32000 per acre with higher densities generally practiced in highly productive environments. When corn is meant for silage, seed rate can be increased by about 10%.
Even though corn is usually seeded at 1.5 to 2 inches deep, in drier conditions depth can be increased to 3 inches. Seed depth of more than three inches may result in reduced emergence affecting the final plant population.

Early Frost
Weather in SD may bring below freezing temperatures periodically in the spring after corn has been planted. Growing point region of corn seedling will be located below soil surface until two leaf stage and will be safe from frost conditions at stages prior to two-leaf. Temperatures below 28° F for several hours however may be lethal to the growing point even though it is below ground. Residue cover, field landscape, and the soil water content can all significantly contribute to the soil thermal behavior. Fields should be assessed at least three days after the frost happened. Seedlings with viable growing point will recover faster when warm weather conditions follow the frost.

Source: David Karki, South Dakota State University 

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