Phosphorus occupies a key place among the major nutrients because of its relative scarcity among the light elements and its essential role in energy transformations in all life forms. Man's use of phosphate reserves has produced both desirable and undesirable effects on the environment. Widespread fertilizer phosphate applications have greatly increased food and fiber supplies for an expanding world population. On the other hand, phosphorus associated with eroded sediments from agricultural lands, as well as phosphorus discharges from urban and industrial areas in sewage effluents and other wastes, are major causes of eutrophication of water bodies.