HELP ME PLZZ, ASAP!!

What types of barriers might prevent trade between countries?

Rivers, Oceans, Mountains, differences in climate, etc.

The Conflict, Race, nature, or other not good for the other is a conflict that can make a country to avoid the other because they're different or weird to want each other.

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.