There are even scholars who think that the South finally gave up because of this. The lack of food broke their back so to speak. Hungry, disease ridden soldiers aren't exactly gung-ho. No matter what the cause they are fighting for.
Look up the 1860s US Railroad map. What little rail connection that tied Fla to the Confederacy were all limited to the Georgia-FLA border. It would be logistically impossible for FLA to be “the bread basket of the confederacy”