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Rehabilitation of Semi-Arid Coal Mine Spoil Bank Soils with Mine Residues and Farm Organic By-Products

A method of rehabilitating coal mine soils was studied under the conditions of a semi-arid climate, lack of topsoil but availability of farm by-products in NE Spain. The objectives of the research were to assess a new method in order to achieve a suitable substrate for the establishment of native vegetation, to evaluate environmental impacts associated with the reclamation process, and to determine the time necessary to integrate the treated area into the surrounding environment. Eight plots (10 × 35 m2) were established in September 1997. Substrate combinations of two types of mine spoil (coal dust and coarse-sized material), two levels of pig slurry (39 and 94 Mg ha−1dry-wt), and cereal straw (0 and 15 Mg ha−1) were applied. Monitoring of select physical and chemical soil properties and vegetation characteristics was performed from 1997 until 2005. The bulk density and the saturated hydraulic conductivity measured did not limit plant development and water availability. Initial substrate salinity (1.37 S m−1) decreased with time and in the long term did not limit plant colonization to salinity-adapted species. Initial nitrate concentration was 298 mg kg−1, but was reduced significantly to acceptable values in 3 years (55 mg kg−1) and the measured pH (7.6) was maintained at the level of initial spoil values. Vegetation cover reached up to 90%. In the treated area, spontaneous vegetation cover (15 to 70%) colonized the nonsown areas widely. In the medium term, vegetation cover tended to be higher in plots with a thicker layer of coal dust material and the higher slurry rate. Soil rehabilitation and environmental reintegration, taking into account soil and vegetation indicators, was possible in the studied area with low cost inputs using residual materials from mining activities and animal husbandry by-products.