The influence of manuring on stable isotopes (δ13C and δ15N) in Celtic bean (Vicia faba L.): archaeobotanical and palaeodietary implications

This paper examines the impact of animal manure on δ 15 N and δ 13 C values in a legume, Celtic Black broad bean ( Vicia faba ). In a field experiment, V. faba was cultivated in plots treated with farmyard manure and pure sheep manure. The results indicate that highly intensive manuring can increase δ 15 N values in beans, stems, leaves and pods. In comparison, manuring had a relatively small impact on δ 13 C values. In terms of palaeodietary reconstructions, the high δ 15 N values in very intensively manured beans (+3 ‰) are equivalent to the trophic-level effect. Based on the experimental results, it is suggested that high δ 15 N values in archaeobotanical remains of V. faba may be attributable to small-scale cultivation with intensive manuring.