Effect of exogenous substances on soil organic and inorganic carbon sequestration under maize stover addition

Soil organic carbon (SOC) and inorganic carbon (SIC) are important carbon reservoirs in terrestrial ecosystems. A large portion of carbon from stover enters the atmosphere after stover return. However, there is little information on soil carbon sequestration during stover decomposition. In this study, a 54-day incubation experiment was conducted in calcareous soil to investigate the effects of wood ash or oil shale application (1.2 w/w%) on CO2 emissions, soil C content, and other soil chemical properties. Four treatments were compared: (i) no maize stover addition; (ii) 1.5% maize stover; (iii) 1.5% maize stover plus 1.2% wood ash; and (iv) 1.5% maize stover plus 1.2% oil shale. Wood ash addition decreased CO2 emission as a result of enhanced SIC sequestration in soil amended with maize stover; oil shale enhanced SOC due to increased carbon input from recalcitrant oil shale. Wood ash addition also significantly increased soil pH and soil microbial biomass carbon. The addition of wood ash to soil may be a potential strategy for promoting inorganic carbon storage and mitigating CO2 emissions after stover return. In addition, oil shale is a very stable C source and oil shale amendment could be an efficient, long-term strategy to sequester organic C in soils.