A medieval hillfort as an island of extraordinary fertile Archaeological Dark Earth soil in the Czech Republic

Archaeological Dark Earth soil is a category of archaeological anthrosols that has gained much attention because it exhibits higher nutrient content and organic matter stocks and a characteristic dark colour, and enables higher crop yields in comparison to neighbouring soil. However, much is unknown about the chemical properties of Archaeological Dark Earth soils in Central Europe. Therefore, we studied a European Dark Earth (EDE) soil, a type of Archaeological Dark Earth soil, in the territory of the early medieval Dřevic hillfort, Czech Republic, aiming to compare the chemical properties of EDE with a control soil unaffected by settlement activities. The black colour of EDE soil contrasted highly with the light grey Cambisol of the control. Soil reaction and total element contents (N, P, Ca, Mn, Fe, Al, Cu, Zn, Sr and Rb) were substantially larger in the EDE soil compared with the control and vice versa in the case of the C/N ratio. Also, the content of plant‐available (Mehlich III) P, Ca, K and Mg was larger in the EDE soil than the control. In contrast to Ca, plant‐available and total P and K were not well correlated. Total element contents are highly suitable for geoarchaeological purposes as enrichment factors can be easily calculated. The increased contents of these elements, together with pieces of charcoal visible in the EDE soil, indicate the deposition of organic waste and biomass ash during the existence of the hillfort. Thus, medieval hillforts can represent extraordinary nutrient‐rich islands in the cultural landscape of Central Europe. The chemical signatures generated by past settlement activities are so intense that they cannot easily be masked by short‐term intensive application of mineral fertilizers. HIGHLIGHTS: Settlement activities increased soil pH and the content of anthropogenic elements. Enrichment by P, Ca, Mn, Fe, Al, Zn, Cu, Sr and Rb may indicate settlement activities. Analysis of total element contents is suitable for geoarchaeological purposes. Application of mineral fertilizers cannot easily mask signatures of medieval settlement activities.