Getting corn off to the right start begins the instant the seeds hit soil. Growers are advised to keep a close eye on soil temperature and planting depth to kick the growing season off right.
Cool soil can prevent good stand establishment. According Iowa State University, corn should generally be planted when soils are near 50°, with temperatures on the rise. Seed absorbs 30% of its weight in water, regardless of soil temperature. Growers will start to see poor emergence in cool soils because seeds will absorb water, but they won’t begin root or shoot growth. If cool conditions continue, the seeds can rot, which could mean the crop needs to be replanted.
Greater yield reduction will be seen from planting too late rather than too early though, according to Iowa State research. Reduced growing degree days (GDD) are to blame; corn needs a certain number of GDDs (dependent on corn’s maturity) to effectively reach tasseling and will also need time for grain fill and dry down.
Carefully weigh soil temperature limitations with GDDs to optimize planting date.
Growers need to make sure the seed is deep enough to establish strong roots and stand up in the wind when planting. Most university Extension publications across the Midwest recommend planting corn 1.5” to 2.5”.
However, Greg Luce, adjunct instructor in the division of plant sciences at the University of Missouri, recommends planting more toward the deeper end.
“I recommend targeting 2” as an excellent depth for corn planting,” said Luce in a recent university publication. Good seed-to-soil contact is essential for plant growth, and he says planting at 2” provides consistent moisture levels and can assist with more uniform stands. In addition, a 2” planting depth can help corn establish a strong nodal root system to support plant structure, nutrient uptake, reduce early season lodging and help the plant endure drought stress better.
Planting at 1.5” or less could leave your corn susceptible to lodging or corn injury from pre-emergent herbicides. Luce says some circumstances, like dry soil conditions, might even indicate planting deeper than 2.5".