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Open‐cast mining of lignite leads to considerable degradation of the natural environment, which then must be reclaimed. The aim of this study was to assess the transformation of Technosols in an area after lignite mining which had been under 40‐year cultivation of alfalfa with grass at various NPK fertilization rates. We hypothesized that 40‐year cultivation of plants caused morphological transformation of the parent material and resulted in differentiation of physical and chemical properties in the profile of the Technosols; fertilization had an added advantageous effect on their properties. The surface layer was transformed into an Ap‐horizon. Under alfalfa, with grass and NPK fertilization, Ap‐horizons demonstrated lower bulk density (BD) (7–11%) and particle density (PD) (1–2%), and higher total porosity (TP) (18–35%), drainable porosity (DP) (2–94%), field water capacity (FC) (11–21%), unavailable water (UW) (4–17%), soil organic carbon (SOC) (80–142%), total nitrogen (TN) (261–330%), available P (39–435%), available K (32–89%), cation exchange capacity (CEC) (25–43%), and soil acidity (Hext) (42–81%) compared to Cd‐horizons. Fertilized Technosols (1NPK, 2NPK), compared with control (0NPK), showed in the Ap‐horizon an increase in SOC (18–35%), TP (8–15%), DP (81–90%), FC (9–10%), P (110–285%), K (14–71%), and TN (0–18%), and a decrease in BD (4–7%). In contrast, fertilization had no effect on the UW, PD, soil inorganic carbon (SIC), CaCO3, available Mg, and pHKCl. The alfalfa and orchard grass played a key role in the reclamation and soil‐forming processes, while fertilization played a supporting role. [ABSTRACT FROM AUTHOR]

Lignite is still one of the main energy sources in many country. Its opencast exploitation causes a lot of changes in the environment. After mining activities are created new and enduring relief forms such as internal and external dumping ground. The dumps consist of rocks conglomerate lying above the exploited mineral. As a result of reclamation, soil develops of this specific material. The aim of this study was to assess chemical properties of soils developing in post-mining areas of the lignite basin in the Wielkopolska region. The study included analyses of the effect of alfalfa (Medicago sativa L.) grown with orchard grass (Dactylis glomerata L.) on chemical properties of soils in 3 mineral fertilisation variants (0NPK - control, 1NPK and 2NPK). The experiments showed that the analysed soils retained the alkaline reaction, calcium carbonate and available magnesium contents as well as CEC from the parent material. The analyses confirmed a significant effect of both Medicago sativa L. and mineral fertilisation on chemical properties of tested soils. Cultivation of Medicago sativa L. (in the 0NPK variant) caused a statistically significant increase in SOC, TN and CEC in the Ap topsoil horizons. Mineral fertilisation additionally enhanced the accumulation of SOC, TN, P2O5 and K2O as well as an increase in CEC value. It needs to be stressed that irrespective of the adopted fertilisation level the investigated soils were characterised by higher SOC, TN, CEC and available Mg contents compared to means values of these parameters reported in arable mineral soils in Poland. [ABSTRACT FROM AUTHOR]