Corn grown as grain doesn't need to be tall, and in many areas, shorter stalks are preferred. They're less likely to blow over, and the corn doesn't put as much energy into producing greenery. On the other hand, if the corn is to be used for silage, the taller the better, because the stalk and leaves are the product.
It wouldn't be unrealistic to have multiple heights, on a modern layout, in adjacent fields. For older periods one might want to research the crops in their area.
The same thing has happened with wheat. It used to be tall, and could be cut by hand with a scythe, without too much stooping. With modern combines, the farmers prefer much shorter varieties. They withstand wind and rain better, are less likely to fall over while being cut, and can put more nutrients into the grain.
