Carbonate C as CaCO3 (also termed soil inorganic C, or SIC) is a principal component of many arid and semiarid soils throughout the world (Dregne, 1976). In reference to soil profiles in southern New Mexico, for example, Ruhe (1967, p. 55) said that the subsoil horizon of calcium carbonate is so prominent that it is the first feature to catch an observer’s eye. The amount of carbonate that forms in an arid or semiarid soil depends highly on soil age (Gile et al., 1966; Hawley et al., 1976). In young soils of Holocene age, only enough carbonate has formed to make filaments or coatings composed of silt and clay sized CaCO3 crystals. With increasing age, the amount of carbonate crystals progressively accumulates, plugging soil pores, engulfing other soil particles, and eventually forming calcic and petrocalcic horizons (Soil Survey Staff, 1998).