Delineation, characteristic and classification of soils containing carbonates in plow horizons within young moraine areas

Abstract

Soil erosion, as a result of which physical, chemical and morphological features of the soil are changing, is an increasingly common problem. The outcropping of deeper horizons of pedons also causes a change in the colour of their surface horizons, which is reflected in aerial photos. Strongly exposed to erosive transformations are agricultural areas. Intensive human activity leads to an increase in ratio of natural slope processes and the movement of soil material by agricultural machinery, which is called human-induced erosion or denudation. The largest transformations within study area - the Chełmża commune, can be observed at the tops of convex hills, where the plow horizons of the strongly truncated soils are mixed with the calcareous parent material (glacial tills). The aim of this study was to determine spatial extent of soils that contain calcium carbonate in plow horizons, based on available orthophotomaps and cartographic materials - topographic maps and a numerical terrain model. More than 700 contours (about 1% of investigated area) of eroded soils potentially rich in the calcium carbonate were delimited. The following criteria were taken into account: 1) very bright brown colour of surface horizons indicating the potential presence of calcium carbonate; 2) proximity of strongly eroded clay-illuvial soils characterized by a dark brown color of surface horizons indicating the exposure on surface of argik horizons; 3) occurrence in places exposed to erosion - on tops of hills and within convex slopes. Field works and laboratory analysis allowed to verification of the contours of potentially calcareous soils. These studies confirmed the high suitability of aerial photos in delimitation of mentioned pedons - 96% of the analysed profiles represented strongly eroded calcareous soils. The average content of CaCO3 in plow horizons was 6.1%. The only genetic horizons of the studied soils are weakly developed A horizons lying directly on parent material. Plow horizons did not meet the criteria referring to colour and/or carbon content of mollik and parent material had too low a calcium carbonate content to designate kalcik horizons. According to the Polish Soils Classification (2019), most of the analysed soils can be classified as weakly developed soils - typical/humic regosols. In one case, due to the strong influence of ground water, the profile was classified as gleysol. The review of archival materials focused on eroded calcareous soils indicates the possibility of occurrence of mollik or/and kalcik horizons and what is connected with it - chernozems, black earths and stagnosols.