Either today's corn hybrids have more vigor and cold starting power to germinate in cooler soils, or seed simply don't pay attention to soil thermometers. Some fields planted early when temperatures were still iffy at 4-inch soil depths emerged before calculations said they should.
At the same time, other fields had problems with emergence. Depth of planting and exact soil temperatures and moisture levels in various areas of the state likely played a role in how quickly corn emerged.
Here's a case in point. Marlon Corwin, New Palestine, in central Indiana, planted corn on Easter Sunday. Eleven days later his seedsman, Ben Alyea, Seed Consultants, Inc., a sales rep in east-central Indiana, checked the field and took the picture shown here. Corn plants were germinating and beginning to poke their heads above the soil. That was only after 11 days in the ground.
You may like to see your corn come up faster than that, but some predictions had said it would take as long as three weeks or more for corn planted around that period in cold soils to emerge.
Their theory was based on the Growing Degree Days that must accumulate to get corn to germinate and get above ground. Bob Nielsen, Purdue University Extension corn specialist, says that number is typically around 120 GDDs. The GDD system is a measure of energy that accumulates during the season that is available to plants for growing.
Related: Good Year to Ask For Cold Germination Test Scores on Corn
Other factors besides better hybrid vigor than in the past may be involved. The line between germinating and not on accumulation of GDDs is a thin line, since GDDs can vary from one area to another. The GDDs are based on air temperature, not soil temperature. Soil temperatures can also vary depending upon soil type and moisture contest.
It will be interesting to see how these early planted fields respond, especially if there are cool weather spells and rain like forecasters expect.