I've traced down a case of lethal blunt trauma inflicted with a potato from 2014 (an involuntary point-blank hit in the head with a potato gun), so the answer is yes, but I don't know of any older non contemporary examples.

EDIT: here you go now; a 1989 british case from London. A man died from a ruptured spleen and of acute respiratory failure resulting from a turnip thrown from a passing car.

Then again, if you are open to lethal blunt trauma from fruit and nuts, Brasil nuts (Bertholletia excelsa) are particularly dangerous as they are densely packed in a similar way to orange segments within a hard and heavy softball-sized wooden fruit borne several tens of meters up in the jungle canopy. There are documented instances of death occuring from getting one on the head (2012 case).

A somewhat peculiar kind of request, if I may say so...

Grain entrapment is often fatal. On average 16 die annually

Death by falling coconut is a very real problem, but the exact numbers are a matter of some disagreement.