This paper summarises the results of the first analytical investigation of the soil chemistry of Asturian Megalithism, an approach which is essential, due to the scarcity of materials conserved in the burial areas. The combination of three analytical techniques enabled this study of the soils from the Cobertoria dolmen (Salas, Spain), a megalithic monument dated at around 3500 BC. The text describes the techniques and results of the analyses made on the corridor, and their relationship with their archaeological contexts. The peaks of some elements closely correspond with the geology of the site while others, especially the phosphorous components, are not common in the natural soils of this area. XRF and ICP-MS analysis showed peaks of this element indicating phosphorus concentrations that cannot be understood without the anthropogenic influence of the use of the corridor. The decomposition of bodies or the organic elements buried here is the most probable reason for these high peaks.