Soil fertility and spontaneous revegetation in lignite spoil banks under different amendments Nuria Pedrol, Carolina G. Puig, Pablo Souza, Rube ´ n Forja ´ n, Flora A. Vega, Vero ´ nica Asensio, Luı ´s Gonza ´ lez, Beatriz Cerqueira, Emma F. Covelo, Luisa Andrade * Departamento de Bioloxı´a Vexetal e Ciencia do Solo, Universidade de Vigo, Campus As Lagoas-Marcosende, 36310 Vigo, Spain 1. Introduction Soil degradation is caused by a series of anthropogenic activities resulting in drastically disturbed soils. Amongst the most commonly disturbed soils are those resulting from coal mining. This disturbance has a drastic, wide-ranging effect on the landscape, together with severe environmental consequences. Reclamation of these soils is necessary in order to minimize the risk of environmental pollution. Mining is defined as a process or activity aimed at removing the desired minerals from their naturally occurring location in the Earth (Paone et al., 1978). In the short term, some minerals have a higher economic value than the soil that covers them. One of the main factors for deciding the most suitable method for their extraction is their proximity to the surface. The surface mining process permits the mineral to be removed through excavation work. Surface mining eliminates vegetation, permanently changes the topography, permanently and drastically alters the geological structure of the soil and subsurface, and disrupts surface and subsurface hydrological regimes. The scale of the impact of surface mining depends on the mining technology used, the extent of the disturbance, the chemical and physical composition of the minerals present and its overburden, the hydrological patterns of the surface and subsurface, and the method of reclamation (Shrestha and Lal, 2006). Mining is an anthropogenic activity, which causes drastic soil disturbances. These disturbed soils have potential for C sequestra- tion through restoration by using organic amendments. The reclamation and revegetation of drastically disturbed soils, including the creation of productive soil and biological resources for C sequestration and the development of profitable and environmentally sound land uses, depend on a sound understand- ing of soil properties under the new ecosystems (Shrestha and Lal, 2006). Coal, one of the important surface-mined minerals, is a key resource for power, heat, industry and transport. Despite its economic importance, mining operations completely remove and stockpile soil materials, resulting in drastic disturbance to the Soil & Tillage Research 110 (2010) 134–142 ARTICLE INFO Article history: Received 21 October 2009 Received in revised form 19 April 2010 Accepted 4 July 2010 Keywords: Minesoils Reclamation Soil limiting factors Soil respiration Plant production Species diversity ABSTRACT In order to study the reclamation of mine sites, the short-term effects of different amendments on soil fertility (at 1 and 6 months) and spontaneous vegetation (at 3 and 6 months) were examined in spoil banks of a lignite mine in Galicia (NW Spain). Experimental plots were established on three spoil banks deposited in 1984, 1988 and 2007, and treated with compost, limestone, NPK or no amendment (control trials). Fertilizer type, time after application and bank age, and their mutual interactions, were found to have significant, early effects on soil quality and fertility in terms of pH, CECe, the organic matter, total nitrogen, and exchange cations contents, as well as on vegetation establishment, composition, and species richness and diversity. The effects of each type of amendment, its ability to correct limitations to plant production and its influence on the successful establishment of spontaneous pioneer species are discussed. Compost gradually corrected P limitations (from 4 to 37 mg kg 1 , in the oldest spoil bank) and significantly improved plant production with respect to untreated spoils (from 1905.1 to 4165.3 kg ha 1 DM). Unlike NPK, compost contributed towards maintaining species diversity and richness. It was found to significantly boost metabolic activity in the edaphic flora, which was estimated from the soil respiration rate as determined by infrared gas analysis (IRGA). Limestone facilitated the establishment of legumes and other dicotyledons, and corrected pH (from 5.3 to 7.0) and Al saturation in CEC (from 37.62% to 0.20%) in the most recent spoils, but produced imbalances in exchange cations (Ca/ Mg = 25.7) due to excessive Ca supply. Based on our results, using compost in recent lignite spoils requires the gradual correction of soil pH with magnesium limestone to avoid Mg limitations. ß 2010 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: mandrade@uvigo.es (L. Andrade). Contents lists available at ScienceDirect Soil & Tillage Research journal homepage: www.elsevier.com/locate/still 0167-1987/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2010.07.005