Farming in which colonial region tended to wear out the soil and created demand for additional farmland to the west

Explanation:

In the South, the lands were held by farmers that had no money and no slaves. In this region, the best lands were owner by rich farmers whom had plenty slaves, this way they were able to produce their food and export goods like cotton, which was highly demand in Europe.

This lands in the South were naturally poor and after a while they hadn't fertility. So, they needed to move the plantation to the west.