δ 13 C and δ 15 N from 14 C-AMS dated cereal grains reveal agricultural practices during 4300–2000 BC at Arslantepe (Turkey)

In semi-arid environments of the Near East water availability and soil fertility are limiting factors for crop growing and land use is locally adjusted to environmental features. In the last decades stable carbon and nitrogen isotope analyses on archaeobotanical cereal remains have been developed in order to reconstruct water and nutrient sources for grain filling. Diachronic studies on isotope records from single archaeological sites may help distinguish palaeoclimatic changes from human choices in agricultural practices, but they are actually missing. We have analysed 13C isotope discrimination (Δ13C) and N isotope composition (δ15N) on barley, emmer and wheat 14C-AMS dated grains from the archaeological site of Arslantepe, Malatya (South-Eastern Turkey). Our intent is to focus on the exceptionally long-term development of agricultural practices at the site from 4300 to 2000 BC. Stable isotope values of cereals show temporal trends in water supplies and manure application. Irrigation was provided to barley crops from 4300 to 3100 BC during the rise of centralised political organisation at the site. Different locations of barley fields are suggested from 3100 to 2000 BC when domestic economies are attested. In addition, the marked increase of barley δ15N values from 3350 to 3000 BC reveals manuring and/or cultivation in pasturelands due to the deposition of animal urea and dung. Wheat could have been grown close to the site, where irrigation water from natural springs was available. Emmer and wheat seem to have been cultivated in the same areas or directly in the same fields. During 3000–2500 BC intercropping cultivation is inferred by low δ15N values. The evidence of mixture crops confirms the increase of pasturelands during herders' occupations and the concentration of crop fields possibly around the site.