https://worldpopulationreview.com/states/alabama/counties

Attached Link above is to a color coded map of population, by county, in AL. According to your theory, counties of the same color should be seeing the same, or at least somewhat similar harvest trends, if fragmented properties and corn are really the route cause of all issues. At a quick first glance comparison, it doesn't appear that that is the case. Overlay the two maps and see what it looks like.