with the potato?
Unfortunately, crucial details such as those pertaining to your question were omitted from this woefully short news story. It is said that the potato was found under the woman's body and so I'm guessing that she was hit with something else, because for her to fall on the object that was used to hit her might be a somewhat difficult maneuver, although that's just my idle musing.
I would imagine also that for an otherwise healthy person to be injured so badly as to cause her to fall unconscious, as is suggested by the story, it would take a fair amount of force. Such force would, I'm guessing, most likely render a typical potato into a more or less mashed state.