Seaweed fertilisation impacts the chemical and isotopic composition of barley: implications for analyses of archaeological skeletal remains

Blanz, M., Ascough, P. , Mainland, I., Martin, P., Taggart, M. A., Dieterich, B., Wishart, J., Sayle, K. L. , Raab, A. and Feldmann, J. (2019) Seaweed fertilisation impacts the chemical and isotopic composition of barley: implications for analyses of archaeological skeletal remains. Journal of Archaeological Science, 104, pp. 34-44. (doi: 10.1016/j.jas.2019.02.003)

Abstract

Fertilisation with animal manure has been shown to affect crop chemical and isotopic composition, indicating that if manuring effects are not taken into account, there is a risk of overestimating consumer trophic levels in palaeodietary studies. The effect of fertilisation with seaweed, a common fertiliser in the past in coastal areas, has been the subject of several hypotheses, but until now has not been studied in this particular context. In this study the impact of fertilising bere, an ancient type of Scottish barley (Hordeum vulgare L.), with 25 t/ha and 50 t/ha seaweed, in comparison to a modern commercial mineral fertiliser and to no fertilisation, was investigated in a field trial on the Orkney Islands, Scotland. Stable isotope ratios (δ13C and δ15N) and elemental concentrations (B, Mg, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Mo, Cd and Pb) of grain, husk and straw samples were determined. Significant differences were found between treatment groups, including increases in δ15N values of 0.6 ± 0.5‰ (average ± 1σ for five replicate plots) in grain, and 1.1 ± 0.4‰ in straw due to seaweed fertilisation. Elevated concentrations of Sr in grain and husk samples (factors of 1.2–1.4) indicate the geographic tracer 87Sr/86Sr may also be affected. Fertilisation with seaweed thus needs to be considered for archaeological interpretations of chemical and isotopic compositions of crop and skeletal material for accurate palaeodietary and provenance reconstructions, particularly in coastal areas. Further implications of these results for studies concerning the effects of sea spray, radiocarbon-dating, and for dietary reconstructions using trace elements are also identified.

• Item Type: Articles
• Additional Information: This research was partially funded by the European Social Fund and Scottish Funding Council as part of Developing Scotland’s Workforce in the Scotland 2014–2020 European Structural and Investment Fund Programme. The contribution of staff from the University of the Highlands and Islands’ Agronomy Institute and the James Hutton Institute to the field trial was supported by Rural and Environment Science and Analytical Services (RESAS) funding from the Scottish Government. GPS geolocation was performed by archaeologists of the Orkney Research Centre for Archaeology (ORCA).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Sayle, Dr Kerry and Ascough, Dr Philippa
• Authors: Blanz, M., Ascough, P., Mainland, I., Martin, P., Taggart, M. A., Dieterich, B., Wishart, J., Sayle, K. L., Raab, A., and Feldmann, J.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Journal of Archaeological Science
• Publisher: Elsevier
• ISSN: 0305-4403
• ISSN (Online): 1095-9238
• Published Online: 19 February 2019
• Copyright Holders: Copyright © 2019 Elsevier Ltd.
• First Published: First published in Journal of Archaeological Science 104:34-44
• Publisher Policy: Reproduced in accordance with the publisher copyright policy