Earth in a tasting note means the smoke reminded someone of dry soil, cellar dirt, or mineral dust. It is a common word on Nicaraguan and some Cuban-seed cigars. It is not a claim that the roller added soil.
Use it as a pointer, not as science. Two smokers will not share a calibration. If a review on Smoke Rings says earth, it means that ordinary association, not a flavor wheel with numbers.
Nearby words on this glossary: leather, cocoa. None of them is a substitute for strength or body.