Corn planters are running
By David G. Hallauer
Meadowlark Extension District Agent
In case you had not noticed, April is here—and that means corn planters are running.
While there is still a lot of corn yet to be planted, that in the ground has already started absorbing water. In fact, the seed will absorb water until it’s approximately 30 percent to 35 percent moisture at germination when it begins growth. That growth does not typically begin until soil temperatures are at or approaching 50 degrees Fahrenheit, so the window we’re in right now is critical to seed survival. If it stays cold and wet, check for emergence issues. If soil temperatures continue to climb and the corn takes off, the seed will forget rather quickly the cool temperature it was planted in to.
How long until it emerges (VE: Emergence growth stage when the coleoptile emerges through the soil surface)? Again, soil temperature is key, as are moisture and seed-soil contact. Most seedlings emerge from 90 to 120 growing degree days from the time it was planted. Plant in cooler soils, and it takes longer to accumulate those heat units to get to emergence. Up until coleoptile emergence, the seed has solely supplied the plant’s energy. That changes when the coleoptile pushes through the soil surface and photosynthesis begins.
The plant is now off and growing, with the plant’s first four to five leaves already existent in the embryo now growing upward through the sheath of the coleoptile as it opens at the soil surface. We may be a bit until this point unless soil temperatures increase a little. Even so, it will not be long until green leaf tips become visible down planted rows.
What happens next? The growing point is still below ground and for the most part well protected from all but the most extremes of temperatures. Leaves will continue to expand, forming collars above the ground as nodal root growth is initiated. Until V6 (six leaf collars), the growing point remains below ground and the plant is supported primarily by the strength of leaf sheaths layered on top of one another.