NK has a 68 day variety that is  Liberty Link variety.  First raised it a couple of years ago - when we had that big freeze in August.  Corn was far along but not good enough for harvesting.

This year it looks real good.  Yield potential is not as good as my 81 day but looks like it will come off a lot drier.

The stuff Marv is talking about would be the cheapest option if you are not considering ever taking it off as grain corn.