Crop Stable Isotopes: New approaches to palaeodietary and agricultural reconstruction

Key points:

  • Investigates the intensity of crop husbandry practices using stable isotope analysis of plant remains from Neolithic and Bronze Age sites in Europe and Western Asia;
  • Assesses the implications of crop manuring practices on palaeodietry reconstructions based on stable isotope analysis of animal and human bone.

This project, in collaboration with the University of Oxford, the University of Bristol and the NERC Isotope Geosciences Laboratory, investigated ancient agricultural practices and land use patterns through the stable isotope ratios of nitrogen and carbon in crop remain, animal bones and human bones. The project explored the effects of manuring on stable nitrogen isotopes ratios and the effects of watering on the stable carbon isotopes ratios in crop plants. Changes in the stable isotope ratios due to management practices determine how to interpret the same ratios in animal and human bones.

This project involved a two-phase approach. Firstly, modern crops were grown in experiments and harvested from monitored farms. The experiments and farm studies were designed to emphasise different levels of field1watering and manuring. The isotopic ratios of these modern crops were compared to their growing conditions to provide a framework for the interpretation of isotopic ratios from archaeological material. This first phase also involved experiments to test the effect of charring and contamination during burial on the isotopic ratio of plant remains.

The second phase involved the isotopic analysis of archaeological field2material from Neolithic and Bronze Age sites in Europe and Western Asia. The intention was to determine whether past societies intensively managed their crops through manuring and irrigation, and elaborate on ancient agricultural practices. The isotopic ratios of these archaeological samples were then compared to those of modern crops grown under different conditions.

Results indicate that charring and chemical pre-treatment (to remove the effect of contaminants) had minimal impact on carbon isotopic ratios and a quantifiable impact on nitrogen isotope ratios. It is possible, then, to utilise nitrogen and carbon stable isotopic ratios from archaeological material to investigate past agriculture. While isotopic ratios are not a precise tool for inferring past growing conditions, especially in the case of carbon due to its close association with photosynthesis which is influenced by a great many factors, they are able to provide useful indications of past conditions. It has already been shown that past cases of intensively managed crops can be identified, and to an extent the level of intensification can be quantified.

Funded by: NERC nerc-logo
Grant Period: 2007 - 2011
Grant Holder: Dr A. Bogaard (PI) (Oxford, Archaeology), Dr M. Charles, Prof. G. Jones (Sheffield, Archaeology), Dr. T. Heaton

(Keyworth, NIGL), and Prof. R. Evershed (Bristol, Chemistry)
Researchers: Dr R. Fraser (Oxford), M. Wallace (Sheffield) and A. Styring (Bristol).

Relevant publications

  • Bogaard, A., Heaton, T., Poulton, P., and Merbach, I. 2007. The impact of manuring on nitrogen isotope ratios in cereals: archaeological implications for reconstruction of diet and crop management practices. Journal of Archaeological Science 34:335-343.
  • Fraser, R., Bogaard, A., Heaton, T., Charles, M., Jones, G., Christensen, B., Halstead, P., Merbach, I., Poulton, P., Sparkes, D. 2011. Manuring and stable nitrogen isotope ratios in cereals and pulses: towards a new archaeobotanical approach to the inference of land use and dietry practices. Journal of Archaeological Science 38:2790-2804.
  • Heaton, T., Jones, G., Halstead, P., and Tsipropoulos, T. 2009. Variations in the 13C/12C ratios of modern wheat grain, and implications for interpreting data from Bronze Age Assiros Toumba, Greece. Journal of Archaeological Science 36(10):2224-2233.
  • Styring, A., Sealy, J., and Evershed, R. 2010. Resolving the bulk δ15N values of ancient human and animal bone collagen via compound-specific nitrogen isotope analysis of constituent amino acids. . Geochimica et Cosmochimica Acta 74(1):241-251.
  • Wallace, M., Charles, M., Jones, G., Fraser, R., Heaton, T., and Bogaard, A. Forthcoming. Stable carbon isotope analysis as a means to infer crop water status, relevance to archaeological research