What happened to a lot of land that owners could not afford to keep after the civil war?

Some, unable to pay their mortgages, lost their plantations when

the banks foreclosed. Some sold out to Northern carpetbaggers.

Those who were able to keep their land realized that they could not

sustain cotton production on an industrial scale without the slave

labor force, because they could not afford to pay living wages.

They developed a system called sharecropping by which the field hands would receive a portion of the crop in exchange for their

labor. The sharecroppers lived on the plantation in their own

shacks. In practice, the system was little better than slavery. the sharecropper had to pay their rent out of their share of the crop,

with very littl left over for anything beyond subsistence.