Human Inputs to the Phosphorus Cycle:
Human influences on the phosphate cycle come mainly from the
introduction and use of commercial synthetic fertilizers. The
phosphate is obtained through mining of certain deposits of calcium
phosphate called apatite. Huge quantities of sulfuric acid are
used in the conversion of the phosphate rock into a fertilizer
product called "super phosphate".
- Plants may not be able to utilize all of the phosphate fertilizer
applied, as a consequence, much of it is lost form the land through
the water run-off. The phosphate in the water is eventually precipitated
as sediments at the bottom of the body of water. In certain lakes
and ponds this may be redissolved and recyled as a problem nutrient.
- Animal wastes or manure may also be applied to the land as
fertilizer. If misapplied on frozen ground during the winter,
much of it may lost as run-off during the spring thaw. In certain
area very large feed lots of animals, may result in excessive
run-off of phosphate and nitrate into streams.
- Other human sources of phosphate are in the out flows from
municipal sewage treatment plants. Without an expensive tertiary
treatment, the phosphate in sewage is not removed during various
treatment operations. Again an extra amount of phosphate enters