Physical restoration of a minesoil after 10.6 years of revegetation

Abstract

Revegetation with different plant species has been a strategy to restore the minesoil profile quality in many countries. However, restoration studies about soils degraded by surface coal mining show that it is not easy a simple task to bring back degraded/mined soil to its near original configuration. Thus, our study monitored the physical restoration of a minesoil by 10.6 years over the same experimental unit used by Pauletto et al. (2016), when the minesoil was with 4.8 years of revegetation. The study was conducted in a coal mining area in Candiota city, Southern Brazil. The minesoil was constructed in early 2003, and the experiment was set up between September/October 2007. The species analyzed were Urochloa humidicola, Panicum maximum, and Urochloa brizantha. Natural soil under native vegetation was used as a reference. In April 2018, soil samples were collected in the 0.00–0.10 and 0.10–0.20 m layers, and the following soil attributes were determined: distribution of the water-stable aggregates in different size classes, tensile strength, soil organic carbon content, bulk density, total porosity, macroporosity, and microporosity. In addition, soil penetration resistance was measured in all experimental areas. The minesoil attributes improvement between 4.8 and 10.6 years occurred in depth, mainly with the cohesive aggregates breakdown, and macroporosity and soil organic carbon content increases. At 10.6 years of revegetation, all perennial grasses improved physical conditions up to 0.10 m depth of the minesoil, with good results than those observed in the natural soil. However, compaction persisted in the 0.10–0.20 m layer, as shown mainly by the higher tensile strength of the aggregates, soil penetration resistance, and bulk density.