After slavery was abolished in the south what type of cheap labor did. plantations rely on?

Sharecropping

Explanation:

With little money or technical training, freed blacks faced the prospect of becoming wage laborers. Because there were so few banks left in the South, it was virtually impossible for former slaves to get loans to buy farmland.  For many freed blacks (and poor whites) the primary vocational option after the war was sharecropping, in which the crop produced was divided between the tenant farmer and the landowner. Sharecropping enabled mothers and wives to contribute directly to the family’s income.

i would go with the last one