What issues contributed most to sectionalism in the United States?

Slavery led to sectionalism in the United States and pushed the country to the brink of war.

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.