About Phosphorus

Phosphate rock is the only economical source of phosphorus for manufacturing phosphatic fertilizers and chemicals. Deposits are widely distributed throughout the world and are generally mined by using surface mining methods. The United States is the world's largest producer of phosphate rock, with annual production of about 45 Mt of marketable rock, accounting for more than 30 percent of total world production. Florida and North Carolina produce the largest amounts, with a combined 85 percent of the U.S. output, followed by Idaho and Utah.

Phosphate rock, when used in an untreated form, is not very soluble and provides little available phosphorus to plants, except in some moist acidic soils. Treating phosphate rock with sulfuric acid makes phosphoric acid, the basic material for producing most phosphatic fertilizers. Phosphatic fertilizers include diammonium phosphate (DAP) and monoammonium phosphate (MAP), which are produced by reacting phosphoric acid with ammonia, and triple superphosphate, produced by treating phosphate rock with phosphoric acid. More than 90 percent of the phosphate rock mined in the United States is used to produce about 12 Mt/yr of phosphoric acid. Domestic consumption of phosphate in fertilizers has averaged 4.5 Mt/yr since 1994.

The United States supplies most of the phosphate fertilizers in the world. Overall, more than 50 percent of the phosphoric acid produced in the United States is exported as finished fertilizers or commercial acid. The United States accounts for more than 50 percent of global interregional trade in phosphates; 90 percent in MAP; and 75 percent in DAP. The United States also imports some phosphate rock for processing -- about 1.8 Mt/yr.