Trace elements in soils and factors that affect their availability

Plants are dependent on the local soil, and the intake of farm animals can be regulated, but man draws his food, and so his trace elements, from the most convenient source. Nevertheless, soil is ultimately the primary natural source of trace elements in animals and man. The factors that control their levels in different soils, their availability to plants, and their contents in different plant species are discussed from the point of view of the amounts available to animals and man.