"Excess items are now put on the ground" space to continue suggestion.

[Zadok]

It makes no sense that my character decides to drop vital items like food on the ground and have it not be on a "SPACE to continue" proc, because I don't stare at the bottom right part of my screen all day to watch if my guy randomly decides to drop my items on the ground.

[MrMotorhead]

What are the conditions for this happening?  I've never seen this message.

[PALU]

This happens when a character is fully loaded (i.e. all inventory slots used up: the weight is irrelevant) and food items are evaluated for decay. It seems the decayed item stack(s) fails to be added to the inventory because it's full because the previous incarnation of that stack (before decay) hasn't been removed yet. The issue would not happen if the previous item stack incarnation was removed before the decayed one was added.
Since the degraded item stack(s) couldn't be added to the inventory it was dropped (and you're in for extra fun if it's on top of a water craft that's also at it's inventory limit, although the craft should no longer explode).