Your corn roots have may have long peaked. You don't have a location and I'm not familiar with you.
The op is in Nebraska and Most of the United States corn belt lies on a very similar line of latitude. That all plant similar maturing hybrids all planted in a similar time frame. So yes it's pretty easy to generalize the root growth of the bulk of the United Stated corn crop.
Edited for the auto correct fix.
Edit added.
Most of the corn in north Dakota is closer to peak depth than from only having seminal roots.
Edited by Hilltop Husker 6/26/2022 13:35
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Big picture.
