Classification of alluvial soils - problematic issues on the examples from South Baltic Lakelands, north Poland

Alluvial soils constitute a group of soils that is very diverse in terms of their genesis and what is the effect of it – most of properties, e.g. organic carbon content, features connected with ground or stag-nating water, development of B horizons or texture. It is also re fl ected in their systematic position. Currently, the Polish Soil Classi fi cation (PSC, 2019) distinguishes as many as 3 types of soils developed from fl uvic materials: ordinary, chernozemic and brown alluvial soils. Some of soils with allu-vial sediments strongly in fl uenced by water but without diagnostic horizons can be also classi fi ed as gleysols or stagnosols. The aim of the article was to check the criteria and to verify completeness of units in the rank of types and subtypes for distinguishing alluvial soils in latest version of Polish Soil Classi fi cation (PSC, 2019). The study was carried out in area covered by Vistulian glaciation in Northern Poland. 87 pro fi les to the maximum depth of 210 cm were studied. 18 pedons belong to cher-nozemic alluvial soils, the most common type (48) was classi fi ed as brown alluvial soils, ordinary alluvial soils occurred 11 times. Moreover, 7 pedons with fl uvic material were classi fi ed as gleysols. Other 3 soils represented organic and colluvial soils. Based on the conducted research some changes in Polish Soil Classi fi cation have been proposed. They are regarding the minimum thickness of fl u-vic materials for classifying alluvial soils, the revision of the humus subtype, the introduction of the type of gleyzemic alluvial soils in gleyzemic order or subtype of alluvial soils in type of gleysols and subtype of waterlogged soils in chernozemic alluvial soil type. The article also addresses important issues of the origin and classi fi cation of B horizons in the studied soils, and con fi rmed signi fi cant usefulness of soil-agricultural maps in determining the places of occurrence of alluvial soils.