Corn plant growth is complicated, and so many things can go wrong

Corn planting continues this week as fields dry out. Over half of the corn acres in our region have already been planted.
Under optimal conditions, the seed will germinate and emerge in five to 10 days. The corn seed requires proper moisture and temperature to germinate.
The shoot will be pushed to the soil surface by a structure called the “mesocotyl.” It will continue to elongate until sunlight hits the emerging shoot.
Light causes a hormonal signal to stop mesocotyl elongation and start unfurling leaves.
If soil temperatures stay cold, or light hits the shoot before reaching the surface, called “open planting slots,” the hormonal signal causes the shoot to unfurl underground or grow in a corkscrew pattern. Either may result in death of the seedling.
The growing point, which is the site of new cell and tissue development, will remain below ground for about three to four weeks, depending on temperature. Leaves will emerge from the center of the stem, called “the whorl,” and unfurl in an alternating pattern up the stem.
When a leaf has reached its maximum extension, a faint line called the collar will be visible on the backside of the leaf. Agronomists use this to establish the growth stage of the corn plant.
Each collared leaf is given a number and the letter V, since the corn is in a vegetative growth stage. When more than half of the plants in a field have a collar on the first emerged leaf, it is at growth stage V1.
Numbers change, as later leaves collar until tasseling.
For example, when the majority of the field has plants with two collared leaves, it is at growth stage V2.
Later leaves will be seen emerging from the whorl, but a growth stage is not given until the collar is visible for a given leaf.
The first corn leaf will have a rounded tip and all of the later leaves will have a pointed tip.
The corn plant will produce about 18 to 20 leaves. No more leaves will form after the tassel has emerged. Critical plant functions have occurred, depending on the growth stage.
The growing point will be protected and below the soil surface until the V6 stage. Plants are about 12 to 18 inches tall when they reach it.
If the growing point gets damaged after the V6 stage, future leaves, ears, and tassels will be injured and destroyed, preventing the plant from completing its life cycle.
Corn plants will develop two root systems.
The first forms from the germinating seed, and the roots are called “seedling” or “seminal roots.”
Seedling roots anchor the plant and take up water. The seed provides most of the nutrients needed by the young seedlings.
Later-developing roots are called “crown roots.”
These roots form at locations, or “nodes,” below the surface and will become the main root system, responsible for nutrient and water uptake for the rest of the growing season.
Crown roots become the main root system about four weeks after planting and replace the seminal roots. Seminal roots gradually die and slough off. If crown roots do not become established in a timely fashion, plants will appear stunted.
Corn plants are generally not considered established until the V6 growth stage.
At V6, the growing point is above the soil surface, crown roots should be functioning, and the potential kernel row number has been determined for the plant.
By V12 growth stage, the potential number of kernels per row and the potential ear size has already been determined. Any stress prior to this growth stage, such as moderate drought stress, may reduce the potential number of kernels per ear.
By tasseling time, the maximum corn factory is in place for the season. The only yield factors remaining are pollination, kernel establishment, and kernel weight.
An individual can assess the effects the environment may have on the corn plant by knowing the growth stage. Sweet corn follows a similar growth pattern to farmers’ field corn.
Early-planted corn was emerging at the end of last week and the first leaf should collar possibly by the end of this week and reach the V1 growth stage.
Remember, the first leaf has a rounded tip.
It will take about three more weeks before this corn reaches the V6 growth stage, depending on temperature.
I encourage farmers to stage the surrounding cornfields and follow its development. Give me a call if you have difficulty determining the growth stage of a plant or field.
Lentz is extension educator for agriculture and natural resources for The Ohio State University Extension Service in Hancock County. He can be reached at 419-422-3851 or via email at lentz.38@osu.edu.
Lentz can be heard with Vaun Wickerham on weekdays at 6:35 a.m. on WFIN, at 5:43 a.m. on WKXA-FM, and at 5:28 a.m. at 106.3 The Fox.

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