Abstract

Cobalt (Co) and iodine (I) are two trace elements that are generally considered to be nonessential for the growth of higher plants.^[1] However, both elements are essential nutrients for animals, particularly in the case of ruminants (sheep and cattle), and deficiencies of Co and I in grazing animals are not uncommon. Cobalt is also essential for nitrogen (N) fixation by micro-organisms such as rhizobium and blue-green algae, and can actually be toxic to plants if present at high concentrations in the soil. Most investigations of Co and I in the soil have concentrated on factors affecting the plant availability of these elements, with the aim of diagnosing potential deficiencies.