From the old times exist the idea that is necessary to let the terrain to "rest" and let it to the nature mercy (in the bible was for a year each 7-years for ex

From the old times exist the idea that is necessary to let the terrain to "rest" and let it to the nature mercy (in the bible was for a year each 7-years for example). Is https://en.wikipedia.org/wiki/Crop_rotation https://en.wikipedia.org/wiki/Crop_rotation So I wonder why not mix both?