Organic Fertilization and Sufficient Nutrient Status in Prehistoric Agriculture? – Indications from Multi-Proxy Analyses of Archaeological Topsoil Relicts

Abstract

Neolithic and Bronze Age topsoil relicts revealed enhanced extractable phosphorus (P) and plant available inorganic P fractions, thus raising the question whether there was targeted soil amelioration in prehistoric times. This study aimed (i) at assessing the overall nutrient status and the soil organic matter content of these arable topsoil relicts, and (ii) at tracing ancient soil fertilizing practices by respective stable isotope and biomarker analyses. Prehistoric arable topsoils were preserved in archaeological pit fillings, whereas adjacent subsoils served as controls. One Early Weichselian humic zone represented the soil status before the introduction of agriculture. Recent topsoils served as an additional reference. The applied multi-proxy approach comprised total P and micronutrient contents, stable N isotope ratios, amino acid, steroid, and black carbon analyses as well as soil color measurements. Total contents of P and selected micronutrients (I, Cu, Mn, Mo, Se, Zn) of the arable soil relicts were above the limits for which nutrient deficiencies could be assumed. All pit fillings exhibited elevated δ15N values close to those of recent topsoils (δ15N>6 to 7‰), giving first hints for prehistoric organic N-input. Ancient legume cultivation as a potential source for N input could not be verified by means of amino acid analysis. In contrast, bile acids as markers for faecal input exhibited larger concentrations in the pit fillings compared with the reference and control soils indicating faeces (i.e. manure) input to Neolithic arable topsoils. Also black carbon contents were elevated, amounting up to 38% of soil organic carbon, therewith explaining the dark soil color in the pit fillings and pointing to inputs of burned biomass. The combination of different geochemical analyses revealed a sufficient nutrient status of prehistoric arable soils, as well as signs of amelioration (inputs of organic material like charcoal and faeces-containing manure).

Soil Scientific Research Methods Used in Archaeology - Promising Soil Biochemistry: a Mini-review

“…Top soils of ancient times are mostly not preserved in-situ but at most archaeological excavation areas or sites. Ancient pits fi lled with former topsoil is the common practice (Eckmeier and Wiesenberg, 2009;Lauer et al, 2013;Lauer et al, 2014). Soil colour is very important to archaeologists because it is a key determinant of age (Jones and MacGregor, 2002).…”

Steroid Biomarkers Revisited – Improved Source Identification of Faecal Remains in Archaeological Soil Material

“…This buried former topsoil material can be preserved in trenches, pits, post-holes or wells [1–2] while still carrying information on the human impact in its chemical signature. Molecular markers may provide indications for agricultural practices outside settlements (off-site features; [2–7]) or for specific husbandry systems, fireplaces, gardens, middens, latrines, and sewage channels inside settlements (on-side features; [8–11]).…”

The Rise of the Anthroposphere since 50,000 Years: An Ecological Replacement of Megaherbivores by Humans in Terrestrial Ecosystems?

“…Improving the recycling of soil nutrients through plowing or adding animal organic waste (manuring) modified the local nutrient balance to increase the productivity and yield of the planted crops (e.g., Bogaard, 2005;Bogaard et al, 2013;Lauer et al, 2014). …”