Recovery of degraded soils by coal mining: quality indicators and plant species

Abstract

The objective of this study was to evaluate the tensile strength and carbon contents in the free light and occluded light fraction of the aggregates in a constructed soil after coal mining and root attributes of grasses used for revegetation. The study was carried out in a coal mining area and plant species evaluated were the Urochloa humidicola, the Panicum maximum and the Urochloa brizantha. In July 2012, 48 soil samples were collected to determine pH in water, base and aluminum saturation, total organic carbon, carbon contents in the free light and occluded fractionsof aggregates and tensile strength of the aggregates. Twelve soil monoliths were collected to determine the root density, volume, length and mean diameter of the studied species. The tensile strength of aggregates can be considered an indicator of the quality of mined soils recovery, since the highest concentration of the grass roots in the surface layer may be influencing the physical structure. The levels of free light and occluded carbon fractions were not appropriate indicators to assess the recovery of degraded areas by coal mining due to negative correlations with root attributes because of the carbon present in the B horizon of the original soil and from the overburden.