Besides studying what is in the soil, archaeologists can study the soil itself for clues about how an archaeological site was formed, what processes buried the site, what kinds of materials may have been buried there, and so forth. Analyses may look at the texture of the soil and its chemical composition (organic matter, nitrogen, phosphorus, pH, etc).
Archaeologists might also study organic residues found on artifacts such as potsherds or stone tools. Using techniques such as Capillary Gas Chromatography, archaeologists working with chemists can sometimes identify the kinds of plants or animals that might have been cooked in a pot, or cut with a stone tool. These techniques are still very new but show great promise for new information.