The soil carbon pool is the largest in the land, affecting carbon balance and soil quality. It consists of inorganic and organic carbon pools. Inorganic carbon includes HCO-3, CO2, and CaCO3, with CaCO3 being the main component. Inorganic carbon affects soil pH, microbial activity, and organic matter decomposition. Organic carbon is a complex mix of fractions, influencing carbon transformation and soil quality. Labile organic carbon can be used by plants and microbes, impacting the carbon balance. Black carbon, stable and derived from combustion, can sequester carbon and improve soil fertility.