Researchers also simulated late emergence in planting corn, says Larson. “Then we harvested the treatment plants individually to see what kind of differences we saw. We had four intervals where we simulated late emergence. Each of those intervals produced about a half-leaf difference compared to the uniform stand. We’re losing a huge amount of yield, 20 to 25 bushels per acre, in the late-planted corn.”

Three different treatments ranged from 7 percent of the plants being late to up to 20 percent being late, he says. In some farmer’s fields last year, 30 to 40 percent of the plants were coming up late, says Larson, so yield differences can be even more substantial than in the research plots.

“What can we do better to get an improved stand? A lot of people think about calendar date, and it obviously can have an impact, but it’s not something that I’d want to hang my hat on. Last year we had extremely cold conditions throughout March, and we had a lot of corn that was planted and sat out in the field for three and a half weeks or more before it came up.

“The calendar date can provide some general guidelines, but we need to be looking more at our environment, how warm and how moist the soil is, looking at real variables that have an impact on seed germination. Keep in mind that soil temperature is the No. 1 factor affecting germination rate and how fast that plant emerges and gets out of the ground.”

The minimum temperature for corn germination is 50 degrees F, says Larson. “We’d prefer to have it up to 55 degrees. As the soil temperature increases, the rate of germination increases exponentially. If the soil temperature is 50 to 55 degrees, it’ll probably take a minimum of three weeks for that corn seed to come up.”

The key, he says, is to go out first thing in the morning and stick a soil thermometer in the soil to see what you’re working with.

“If you have a soil temperature of more than 55 degrees first thing in the morning, you can almost guarantee yourself that plant will be up within a two-week period, and your likelihood of having uniform emergence is much, much greater than if the soil temperature is below 50 degrees.”

Another general guideline is to check nighttime low temperatures, he says. The soil temperature generally will be close to the nighttime lows.

“The corn seed has to be in the ground 24 hours per day, so if it gets down to 40 degrees at night, it may have sufficient temperature for emergence only six to eight hours each day. It’ll be dormant the rest of the day, and a lot could go wrong.

“Normally in the South, soil moisture is our biggest limitation during planting season. You may have dry-enough soil moisture in part of the field, but where the soil is heavier, it might be too wet for optimal planting when the planter goes through the field.