ABSTRACT
Small amounts of other elements may be necessary for an individual plant species to complete a life cycle, but those represent the major plant nutrients. Plants absorb some elements not known to be required by them but which are necessary for animal nutrition. This chapter discusses all of these elements, and several others known to be toxic to plants and/or animals. Some biologically active elements are required for plant growth in large quantities that they are referred to as macronutrients. These include nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. The exact nature of the mechanism by which potassium functions within plants is not known but it is considered essential for almost all plant physiologic activities. Thus, an accurate assessment of available soil sulfur is difficult to determine and subject to question, much like plant-available soil nitrogen and phosphorus. Hazardous waste sites associated with mining and metal processing facilities are replete with examples of elevated arsenic levels in soils and water.
