Over the weekend, I started to get the age old question, “Should we start planting corn?” Last year, we were really focused on cool soil temperatures and this was well warranted. Some chose to start planting during mid-April despite the cool soil temperatures. Others waited, but then the rains came and kept us out of the field. Many think that cool soil conditions are a major risk factor (soil temperatures below 50 degrees F.) when planting corn, but we must not forget to consider precipitation and the extended forecast. Learn About This Weather Pattern Before You Plant is a recent blog that outlines the weakening of the El Nino and how "This situation often leads to cold and wet Aprils across much of the country, including the Plains and Midwest, many times after an unusually mild winter.”
The main source of problems to corn stands from the time it is planted until the seedling emerges are:
- soil moisture (excess or lacking)
- inadequate soil aeration (ex. compaction, saturation)
- soil temperatures (usually cold)
- or a combination of all these factors above
- The most important factor to consider is planting into a favorable seedbed. No need to "mud it in" and cause field compaction to occur. This was a huge issue last year! In disparity to plant in between the rains, many did “mud it in” and many were ripping fields in the fall as a result.
- The biggest risk factor to corn emergence is planting into soils that are near 50 degrees F. and then having prolonged wet soil conditions, because most replanting of corn occurs when seeds or seedlings are deprived of oxygen. More information at Evaluating Corn Stands after Excessive Rain.
- In reality, if you are going to plant early, planting corn into cooler soils, when seeds are less likely to germinate, then have wet conditions, is perhaps a better scenario. To date, soil temperatures are hovering around 40 to 45 degrees F. Seed germination occurs when air temperatures reach 68 to 77 degrees. It will take around 110 to 120 Growing Degree Days (GDDs) for corn to fully emerge, so be cautious, because the longer that seed stays in the ground, the more likely it is for problems (mother nature and pests) to occur.
- Frost injury to the corn seedling after emergence is not usually a problem. When a corn seed first germinates the, the seed absorbs 30 percent of its weight in water and thus, the radical or (first root) emerges within two to three days in warm soils with adequate moisture or much longer if soil temperatures hover at or below 50F. Some sources say at this stage of the germination game, soil temperature swings have no effect on growth and emerged seedlings are relatively resistant to cold. Later, the growing point remains below ground.
- But, what about corn cold imbibitional chilling damage? One of the main theories is that this injury occurs when there are soil temperatures swings (some sources say less than 50 degrees and others say at least 41 degrees or below) after germination (24 to 36 hours after the seed has (imbibed) absorbed water). If the cells of the corn kernel are too cold, they can rupture, thus the kernel can become swollen and any growth of the kernel can cease. Cold imbibitional symptoms may show up as delayed emergence, failure of emergence, leafing out underground, or stunted growth and distorted leaves of the newly emerged seedling.
The current soil temperatures for Illinois and Missouri can be easily found at www.burrusseed.com.