Depends on what is planted. Most of the time however, crop rotation is used to keep fields as fertile as possible. The result is a field that can be used over and over, with less concern for the environment and maintenance. One reason people moved west was to find NEW fertal soil, because they lacked the ability to consider crop rotation. I guess the point is though, that crops will grow better, and many harmful incects will have trouble adapting to constant change.
