Cropmarks in stands of cereals, legumes and winter rape indicate sub-soil archaeological features in the agricultural landscape of Central Europe

Small-scale variability in biomass production of crops (cropmarks) can be used for mapping of former human activity in the agricultural landscape. The aim of this study was to assess the suitability of the most frequently planted crop species for identification of sub-soil archaeological features in the agricultural landscape in the NW of the Czech Republic. During 17 years of aerial surveys, 635 archaeological localities were discovered based on cropmarks. The mean number of archaeological features in each locality was approximately 30, ranging from 1 to more than 300. The age of the features ranged from 7500 years (Neolithic) to the modern day, the latter having no archaeological importance. In the contemporary agricultural landscape, the density of archaeological localities was 0.59 per km2. Over all discovered localities, 95% of archaeological features were positively cropmarked and only 5% were negatively cropmarked. Point features like settlement pits, semi-sunken buildings and graves were substantially more frequent than linear features such as ditches, palisade fortifications and dikes. Negative and positive cropmarks were the best developed in stands of cereals, especially in barley, followed by wheat, rye and oat from tillering up to full ripeness. Lucerne was the best crop for indicating sub-soil archaeological features during the dry summer. Cropmarks in winter rape were substantially less conspicuous than those in cereals. Sugar beet, potatoes and maize did not indicate the presence of any archaeological features.