Traces of German and British settlement in soils of the Volta Region of Ghana

Abstract

Can less than a hundred years of past settlement activities in former European settlements substantially increase the concentration of elements and result in the formation of African Dark Earth soil is a question not addressed. We performed multi–element analysis of Africa Dark Earth soil from a late 19th to mid–20th century CE former German–Togoland settlement, Ziavi–Galenkuito in the Volta Region, Ghana. Relatively neutral reaction and black color of soil mainly from charcoal inclusion in the settlement site contrasted highly with moderately acidic brown Ferric Acrisol in the control located on the same metasedimentary/Voltaian bedrock. Organic C and total N, P, K, Ca, Mn, Fe, Cu, Zn, Sr and Rb concentrations were substantially increased and vice–versa for the C/N ratio in the 0–40 cm layer of the settlement soil compared to the control without settlement activities. The concentrations of plant–available P, K, Ca, S, Fe, Cu and Zn were higher in the settlement soil in comparison to the control. The increased concentrations of the elements mentioned above resulted in the disposition of organic waste and biomass ash. Significantly higher concentrations of total and plant–available elements in 0–10, 10–20 and 20–40 cm layers of settlement site compared to their respective control suggested that chemical signatures from past settlement activities can be determined even in the upper soil layer. Positive correlations between the concentration of P and K, Mn, Sr, Fe, Ca, Zn, Rb, Cu implied that these elements were indicators of past settlement activities. The concentrations of total and plant–available P, K, Ca, Fe, Cu and Zn were well correlated; however, total elements concentrations are much suitable for geoarchaeological purposes as it is easy to calculate enrichment factors. We concluded that intensive human settlement activities in even <100 years resulted in the development of Africa Dark Earth soil with a substantial accumulation of elements.