Fertilizer 101

Phosphorus and Fertilizer Products

The phosphorus in most commercial fertilizers comes from phosphate rock, found in fossil remains originally laid down beneath the oceans and later lifted up with land masses. Fertilizer manufacturers mine deposits of phosphate rock to provide P for a variety of commercial fertilizer blends.

The P in fluorapatite is practically unavailable to crops in the form in which it comes “out of the mine” (although in the past, very high-grade phosphate rock was ground and applied more or less as found). Phosphorus fertilizers are generally classed as being either thermal-processed or acid-treated. The latter are considered to be more commercially important.

The most widely used commercial phosphorus fertilizer products in the United States are the ammoniated phosphates, diammonium phosphate (DAP) and monoammonium phosphate (MAP). Nearly 60 percent of the P applied in 2007 was either direct application DAP or MAP. DAP and MAP are also used to provide the P in many fertilizer mixtures and bulk blends. Thus, ammoniated phosphates account for the lion’s share of total P use. Other commercially important P products include various phosphoric acids and liquid ammonium polyphosphate. Other phosphate products include normal superphosphate and triple superphosphate.