Effect of fly ash on carbon mineralization of biochar and organic manures added to mine spoil

Mine spoil is deprived of organic carbon. Reclamation and re-vegetation of mine spoil initiate photosynthetic carbon fixation and add soil organic matter. Fly ash (FA) generated from coal-fired power stations can be used for reclamation of mine spoil. Our research was aimed to assess the effect on FA on carbon mineralization of organic manures and biochar added to mine spoil. Incubation experiments were conducted to assess the carbon mineralization of farmyard manure (FYM), chicken litter (CL), plant litter (PL), and biochar (BC) added to mine spoil in the presence and absence of FA. After 1 year of incubation, the cumulative-CO2 emission was lower for the FA-added mine spoil and it was higher for PL (4.42 vs. 5.09 g-CO2-C/kg soil, with and without FA, respectively) and CL (3.75 vs. 4.07 g-CO2-C/kg soil) followed by FYM (1.86 vs. 1.97) and BC (0.67 vs. 0.54 g-CO2-C/kg soil). The labile C pool was significantly lower for FA-added mine spoil, whereas the stable carbon pool was higher in FA-added soils: FYM (1.4 vs. 0.6 g-CO2-C/kg soil) and CL (2.20 vs. 3.17 g-CO2-C/kg soil). Substrate-induced respiration, microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were significantly higher under PL, CL, and FYM. FA increased MBC, but decreased DOC. Overall, FA decreased-CO2 emission from mine spoil probably due to the interaction of organic matter with the surfaces on FA and the resultant physical protection against microbial decomposition.