Using δ 15 N analysis of soil organic matter in two deserted medieval villages and their agricultural land in different environmental conditions in the Czech Republic, the aim of this study was to study the application of organic fertilizers on medieval agricultural land.

The study was performed in the villages of Roudnička (430–455 m a.s.l.) and Spindelbach (800–880 m a.s.l.), both established in the 13 th century and deserted in the 15 th century and covered by Norway spruce ( Picea abies ) forest at present. Soil samples of humus horizon (Ah) were collected in close vicinity to the former buildings and in the deserted medieval fields in autumn 2011.

No significant differences were recorded in δ 15 N among the soil samples collected in close vicinity to the ruins of the buildings or in the former field in Roudnička. Despite there being no significant effect in terms of the position, there were clear trends with the lowest values of δ 15 N recorded in close vicinity to the buildings, and the highest values recorded in the former field. The δ 15 N signature was significantly higher in close vicinity to the ruins of the buildings than in the former fields in Spindelbach in all probability indicating deposition of organic fertilizers connected with livestock breeding close to the houses. In both deserted villages, δ 15 N signature significantly decreased on the former agricultural land with the distance from the village indicating a decrease in deposition of organic fertilizers with the distance from the farm buildings.

We concluded that δ 15 N signature generated by medieval farming practices can be detected in contemporary forest soils and δ 15 N signature can be thus used for the study of ancient farming practices.