Impact of addition of silt from brown coal on basic physical and water properties of the topsoil developed from post-mining land of Konin brown coal mine

Post-mining land created as a result of the deposition of the strippings from Konin Brown Coal Mine (Konin BCM) is being rehabilitated in accordance with principles of the target species concept developed by Bender. The rehabilitation technology realised in accordance with this concept is based on the enhancement of soil chemism and improvement of physical properties supporting the development of vegetation cover and stimulating biogeochemical processes. The basic soil-forming factor in this concept is the anthropogenic factor integrating the action of biotic and abiotic factors into a consistent, mutually supporting system of rehabilitation actions and activities whose aim is to transform, within the period of 10 years, this specific maternal material into soil. One of the forms of integration of the anthropogenic factor into the composition of the solid phase of the developing soils was the addition of brown coal dust - a by-product created in the production of briquettes. The usefulness of brow coal for fertilisation purposes stems from the composition of its organic matter as well as specific physical, physico-chemical and chemical properties. The objective of the research project was to determine the effect of the addition of brown coal on major physical and water properties of anthropogenic topsoil 18 years after application. The research object was situated on the experimental plot of the Department of Soil Science and Restoration established in 1978 on post-mining land of Patnow Mine internal dumping ground. The experiment comprised two variants. Variant A control comprised the area on which, from 1978, the applied treatments were consistent with Bender's concept of target species. In the case of variant B, on an experimental area subjected to restoration treatments for 14 years, fertilisation with brown coal dust in the amount of 1000 t.ha(-1) was applied in 1992. The following four fertiliser combinations were employed in this variant: 0 NPK (1); 100 kg N, 80 kg K2O, 40 kg P2O5 (2); 200 kg N, 80 kg K2O, 40 kg P2O5 (3); 300 kg N, 80 kg K2O, 40 kg P2O5 (4). In both experimental variants, winter cereals were cultivated. Straw and other plant residues were ploughed under every year. In 2010, soil samples of intact and broken structure (V=100 cm3) were collected from the topsoil of individual plots for laboratory exanimations. The following parameters were determined: total carbon and nitrogen, texture composition, solid phase density, soil density, total, drainage and differential porosity, hygroscopic moisture content, maximal hygroscopic capacity, filtration, soil water binding potentials, potential and effective useful retention. It was concluded, among others, that the selected major physical, chemical and water properties of the arable layer of the agriculturally rehabilitated soils in accordance with principles of the concept of target plants were at the typical level characteristic for cultivated soils of similar texture and total carbon content. The addition of brown coal to the top layer of soil developing from post-mining land caused: a decrease in the soil density as well as the density of its solid phase, increase of total porosity, increase in proportions of mezo- and micropores, enhancement in the value of hygroscopic moisture content as well as maximal hygroscopic capacity. In the examined soils, together with the increase of the applied nitrogen fertilizer doses, the content of total carbon as well as C:N ratio narrowed. This was probably due to a faster rate of organic matter mineralisation. Long-term nitrogen fertilisation comprising four combinations failed to affect diversification of the total nitrogen content. In the case of soils with the addition of brown coal, the availability of production water was extremely low. On the other hand, the content of water available for plants but bonded with strong forces was high