By Greg LaBarge, Ohio State University Extension
Determining seed planting depth is one place to start when diagnosing corn emergence issues. We can use the corn plant’s pattern of emergence and root placement to determine the seed depth placement of the planter. The mesocotyl is the white tubular stem-like plant part located between the kernel and the base of the coleoptile is the key to determining planting depth. The mesocotyl pushes the coleoptile or “spike” toward the soil surface.
Growers can diagnose seed placement problems by digging up and observing the mesocotyl length after emergence. Since the plant places the crown at three-quarters inch deep, measure the length of the mesocotyl from the crown to the seed and add three-quarters inch to determine seed placement. The mesocotyl is pretty resilient. I have dug up plants in mid-vegetative to early reproductive stages and found the mesocotyl with the empty seed attached to the crown.
Determining seeding depth after emergence helps measure planter performance and troubleshoot corn emergence issues. Seeding depth interacts with soil conditions, temperature, and moisture resulting in various emergence problems. For example, seeding depth, conditions for seedling growth, and cell growth inhibitor herbicides can interact, resulting in herbicide injury. Bob Nielsen, Purdue University, has a great 2022 article discussing corn emergence issues that you can find at https://go.osu.edu/emergence.