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Rustification as a collateral process in clay-illuvial soils of northern Poland

The lessivage (clay-illuviation) and rustifi cation are among the two most common soil-forming processes in soil cover of Poland. The horizons of illuvial accumulation of the clay fraction are observed in approx. 50% of Polish soils, while rusty soils constitute about 14% – that is almost half of all sandy soils in the country. Due to the different conditions of both processes – mainly lithological in nature – they are generally perceived as separable phenomena leading to the formation of two different types of soils – clay-illuvial soils (WRB – Luvisols) and rusty soils (Brunic Arenosols). However, in some soil profi les, especially those formed in sands covering glacial tills, the effects of both of these soil-forming processes are observed. The aim of the study was to characterize the soils with the features related to the illuviation (lessivage) of the clay fraction and the accumulation of iron sesquioxides in the form of iron coatings formed in-situ in the sandy material (rustifi cation). In order to check how often these processes take place simultaneously, 29 soil profi les with a texture enabling the simultaneous acting of both processes in the young glacial areas of northern Poland were analyzed. In as many as 66% of cases, the presence of features related to both processes were found. The lack of the rustifi cation was recorded predominantly in arable soils – often shallowed by erosion or with a clear stagnation of water in the eluvial horizons. Most of the studied soils were classifi ed as texturally contrasted rusty clay-illuvial soils (WRB – Abruptic Luvisols (Brunic)) or lamellic rusty clay-illuvial soils (WRB – Lamellic Luvisols (Brunic)). Thus, both processes in soils developed from cover sands underlying by glacial tills are complementary to each other, and the profi les of A-Bv-Et-2Bt-2Ck morphology (designation of horizons according to Polish Soil Classifi cation (PSC, 2019)) should be perceived as fully formed and undisturbed by human activity. Keywords