Abstract
The aim of the research was to determine the effect of lithogenic and pedogenic processes on the formation of Luvisols from the area of Vistula glaciation on the base of profile distribution of iron oxides and total iron in relation to texture and physicochemical properties. The indices of weathering of the soil material in genetic horizons were calculated, and changes in the content and forms of iron oxides were evaluated. The predominant type of soil in the study area is Luvisols under agricultural use, formed from silt formations on loam. The analyses were made applying the following methods: grain size composition using the sieve method and hydrometer method, the interpretation of the results was performed according to the World Reference Base for Soil Resources classification, the pH of soils was measured with the potentiometric method, C-organic with the Walkley-Black dichromate method, the content of the following iron forms was determined (total iron (Fet) after the mineralization of soils in the mixture of HF and HClO4 acids), free iron oxides were extracted using dithionite-citrate-bicarbonate method, and amorphous iron oxides after the ammonium oxalate extraction (using the Philips 9100PU apparatus). The clay mineralogy was estimated by X-ray diffraction analysis. It was observed that total iron enrichment occurs in argic horizons accompanied by iron depletion in luvic horizons, while the profile distribution of iron is similar to the distribution of clay. The (Fed/Fet) ratio indicates a low degree of weathering; the highest values were observed in argic (Bt) horizons, which confirms the effect of the process of pedogenesis on the value of that index. In the soils investigated, crystalline iron oxides generally dominate over the amorphous forms. The mineralogical composition of clay fraction separated from the upper part of soils was different as compared to the underlying material. The results of the study showed that iron contents (together with the other indicators) and its forms can be used to distinguish soil layers of different origin. The depth distribution of Fed, Feo and Fet within soil profiles indicates that the soil material may be of different lithogenic origin in the studied pedons.
Highlights
IntroductionThe Luvisols is formed during the Kujawy-Dobrzyń subphase of the Vistula glaciation demonstrating a morphological profile variation, which could be due to the processes of lithogenesis and pedogenesis
The Pleistocene deposits formed as a result of Scandinavian continental glaciations cover much of northern and central Poland
The depth distribution of Free iron oxides (Fed), Feo and Fet within soil profiles indicates that the soil material may be of different lithogenic origin in the studied pedons
Summary
The Luvisols is formed during the Kujawy-Dobrzyń subphase of the Vistula glaciation demonstrating a morphological profile variation, which could be due to the processes of lithogenesis and pedogenesis. The iron compounds, especially their complex associations with humus colloids, determine the profile distribution of other elements (Tack et al 1997) in soils. They affect the colour of soils and are indicators of their properties (Kabata-Pendias and Pendias 2010). The colour of goethite changes from yellow for crystals in the micrometre size range to dark brown for crystals of ca. An increasing Fed/Fet ratio reflects the progressive weathering of Febearing minerals with time (Arduino et al 1986)
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