Traces of ancient agriculture in the soil around the archaeological sites (A case study from Northern Caucasus, Russia)

The article describes the results of research of traces of ancient and medieval agriculture in the vicinity of the settlement Podkumskoe-3 of the Alan culture (5th-8th centuries) in the Northern Caucasus, Russia. Methods of soil science, soil microbiology, archaeology, and archaeobotanical analysis were used. Soil sections were made at different distances from the settlement (up to 1200 m). It is shown that ancient and medieval agriculture left a noticeable trace in the soil in the form of ceramics, charred grains, and straw of cereals, and also led to changes in the chemical and biological properties of soils within the potential economic zone of the site. The soils within the 500-600-m zone around the settlement Podkumskoe-3 bear traces of plowing and fertilizing in the Early Middle Ages. At a greater distance from the settlement, traces of medieval agriculture disappear, but everywhere there are traces of plowing in the Late Bronze Age in the form of ceramics of the Koban culture. The most reliable indicators of ancient agriculture are, in addition to ceramics, coals and charred remains of grains of cultivated cereals and straw. However, charred grains and straw are preserved only in the lower layers of the soil, corre-sponding to the first stage of plowing. In the more recent layers, which were plowed for a long time, the coals are destroyed. The fertilization zone is determined by the abundance of thermophilic microorganisms. They got into the soil with manure after self-heating of animal dung during decomposing. This indicator well marks the fertilization zone in the Early Middle Ages and shows a close correlation with the ceramics of this time. In soils where only Bronze Age ceramics are present, the number of thermophilic bacteria is at the level of background soils.