Plagganthrepts in northwest Russia? Genesis, properties and classification

To clarify the properties, genesis and classification of typical anthropedogenic soils of St. Petersburg area, exemplary five profiles were thoroughly investigated. The soils are characterised by humus-rich, well-structured and biologically active anthropedogenic epipedons, reaching depths of 52 and 55 cm. The texture, the mineral distribution and the XRD analysis confirmed the multiple geological composition of the profiles. The bulk densities of the anthropedogenic epipedons were 1.0–1.3 g cm−3 and down to 1.9 g cm−3 in the underlying horizons. The pH values were 4.9–6.8 (CaCl2). Small lime amounts were found in two cases. The Corg contents were 23.5–74.0 g kg−1 and the N contents 2.0–3.9 g kg−1 in the anthropedogenic horizons and 0.8–4.9 g kg−1 and 0.1–0.3 mg kg−1 in the underlying ones. Decreased humus contents in the root zone indicated degradation processes. The base saturation was mostly 100% and the CEC 9.3–17.1 cmolc kg−1 in the top and 3.0–9.3 cmolc kg−1 in the subsoils. The total P contents were 884–1835 mg kg−1 and the citric acid soluble P content 321–776 mg kg−1 in the anthropedogenic epipedons and 189–355 and 46–321 mg kg−1 in the underlying horizons. Thus, the anthropedogenic St. Petersburg soils showed distinct similarities to the Plagganthrepts of northwest Europe in respect of Corg enrichment, surface raise and P enrichment. The same is true regarding the main management aims: increase of soil fertilisation combined with an overcome of lacking bedding materials. Hence, the genesis and most properties of the anthropedogenic St. Petersburg soils support a classification as Agrosems (Russian taxonomy) Plaggeneschs (German taxonomy) Plagganthrepts (U.S. taxonomy) or terric Anthrosol (World Reference Base for Soil Resources [WRB] taxonomy). But the required thickness of the anthropedogenic epipedon is barely achieved. Thus, Plagganthrepts occur as small patches, which may even decrease, because of soil degradation.