I use standing corn a lot to get into spots both AM and PM. I would never walk an edge of a tree line without being in the corn. While they like bedding in the corn... they love bedding and milling right along the tree's edge that borders a standing corn field. It would be suicide to walk inside a tree edge to get to a spot even for a PM hunt.
The deer that do bed in the corn... usually bed in cattail sloughs in the corn field in my area. I know my area very well. You use the wind to work you way though the corn so it doesn't blow your scent into these bedding spots. Yes... you may bust an occaisional deer but that can happen no matter how you walk into an area especially in the morning when we are stumbling around in the dark.
If the fields have been harvested... I rarely use them for access in the mornings, but sometimes use them for PM hunts if I go in really early and can stay out of sight. Without the standing corn... it is a different ball game.
It really depends on a person's situation on how to hunt an area whether it be AM or PM. Hard to take advise when someone uses a blanket statement... don't hunt it in the AM when you only have the AM to hunt. If I had a lot of time to hunt and could control who hunts the area... common sence says to play it safe and stay out. I don't have that luxury so common sense says to figure a way to hunt it before someone else wrecks the spot. In my area... someone else wrecking my spots is a given. It might as well be me and I ain't afraid to push it !!
Tim