Soils comprise the planet’s largest terrestrial carbon (C) pool, containing both organic and inorganic C. In recent times, the significance of soil inorganic carbon (SIC) has been relatively overlooked compared to soil organic C (SOC). One of the objectives of this chapter is to raise the awareness of the SIC pool in soil. In order to avoid confusion, the term “soil C” will be used to mean SIC or SOC or both.