09 Oct 2006

Some Things to Know About Phosphorus

Some Things to Know About Phosphorus

Phosphorus (P) is all around us. Small concentrations are present in all lakes, streams, oceans and seas. It is in soils, rocks, minerals, plants and animals. It is present in every living cell and is essential to all forms of life.

Phosphorus is the second most abundant mineral in the human body, surpassed only by calcium. It makes up about one percent of total body weight. On average, adult males and females contain about 720 and 540 g of P, respectively. Nearly 80 percent of the P in humans is found in bones and teeth. The remainder is widely distributed in the body in soft tissues. Phosphorus is seldom deficient in human diets.

How can we be sure we are getting enough P? By practicing good health habits, which include eating right. Nature supplies us with an abundance of P in the foods we eat. Some foods high in P are meats, vegetables, fruits, nuts, grains, and dairy products. For example, 227 g of yogurt (1 cup) contains 214 mg of P and 28 g of almonds (1 ounce) has 134. Eating appropriately sized portions of a variety of nutritious foods is our best way to get all of the vitamins and minerals we need while staving off both malnutrition and obesity.

Plants require relatively large quantities of P. For instance, a 10 metric ton/ha (160 bu/A) corn grain crop takes up about 42 kg P/ha (37 lb P per acre). Nitrogen (N) and potassium (K) are the only other essential plant food nutrients taken up in greater quantities than P. Phosphorus is involved in numerous plant functions, especially those requiring energy. The sun’s energy, used in photosynthesis, would not support the necessary plant functions if P were not present in ‘energy packaging’ compounds. Phosphorus is indeed the energizer in food production by plants.

Phosphorus is used to fertilize crops around the world. The most common source is phosphate rock, most of which is recovered for processing by surface mining techniques. The known world reserve base of phosphate rock exceeds 40 billion metric tons (50 billion short tons)…enough to last hundreds of years. The U.S., North Africa (Morocco and western Sahara), and China produce about 60% of the phosphate rock used in making P fertilizers. Animal manure and other by-products contain P and should also be used responsibly to meet crop needs.

Phosphorus and N are two essential plant nutrients that can have a negative impact on water quality if they are not managed correctly. Care must be taken in their use to ensure that as much as possible is taken up by crops or kept in fields where they are applied. To be lost, P in the soil must be transported off site, either by erosion, runoff, or in extreme cases, leaching. Consequently, high soil P levels alone do not pose an environmental hazard. Soil conservation practices are the best defense against unwanted P losses.