Physico-Chemical Characterization and Mine Soil Genesis in Age Series Coal Mine Overburden Spoil in Chronosequence in a Dry Tropical Environment

Abstract

A pre-requisite to any revegetation plan, as well as restoration of degraded land is the knowledge of physicochemical characterization, which is crucial for prediction of ecological succession for mine overburden spoil, including soil texture, hydrological regimes, pH, organic carbon, nitrogen and extractable phosphorous. Effects of mining activities are markedly adverse, because many of the beneficial soil characteristics may require a long span of time to develop through pedogenic processes, in order to reach the native forest soil condition, which evaluates the degree of functional microbial processes for ecosystem recovery, and used as an index of the progress of soil genesis in mine overburden spoil. Mine spoil samples collected from six different age series overburdens showed progressive increase in clay (%) (r=0.982, p<0.001), water holding capacity and organic carbon, which indicates the development of soil structural stability, aggregation with the increase in age of overburden spoil. The pH of spoil samples was noted to be in acidic range (6.11-6.87). Approximately, 93.7% variability in clay (%) among different mine spoils can be explained due to the variation in organic carbon. The organic carbon, nitrogen and phosphorous content showed an improvement of 2 mg C/g spoil, 161 µg N/g spoil and 8 µg P/g spoil, respectively, over a period of 10 years. Thus, the net annual accumulation rate for carbon, nitrogen and phosphorous on hectare basis amounted to 255 kg C/ha/yr, 20 kg N/ha/yr and 1 kg P/ha/yr, respectively. Further, it was estimated that the mine overburden spoil to attain the soil features of nearby native forest soil, at study site through the process of reclamation, shall take approximately 28 years.