The availability of chemical elements from soils to plants and ultimately to animals consuming them has been investigated by scientists for centuries. Evidence has accumulated to support the theory that plants respond directly to changes in the activities of ions in the soil solution and only indirectly to the quantities of each element in soil which maintains the respective activities within the soil solution. Soil management involves changes in the available forms of each element in order to obtain the required range of activity to meet plant requirements. The Baker Soil Test™ (BST) is a new approach to soil testing which provides an activity measurement (intensity), a quantity measurement (extensive), and for some samples the total sorbed quantity of metals.