Cobalt [Co, 27]

Cobalt (Co), a metal of the group 9 in the periodic table of elements, reveals both chalcophillic and siderophillic tendencies. Soil-forming processes, which differ in various climatic zones, have a great impact on Co distribution in soil profiles. Higher Co contents of surface layer of soils are in arid and semiarid climatic zones, whereas very low Co contents are in light soils, in humid climatic zones. Cobalt speciation in soils depends on several factors, of which Eh and pH play the most significant role. Reduction of soil Eh and decreased soil pH elevate the Co mobility. Soluble species of radiocobalt may be released from some nuclear reactors to water, and therefore its contents may increase in the future. Cobalt deficiency inhibits plant growth, mainly of various legumes. Its deficiency in fodder plants is considered mainly from the viewpoint of ruminants requirement, as it is the main precursor of vitamin B₁₂.