PlantPhosphorus (P) is another one of the “big three” primary nutrients. Phosphorus is involved in many processes critical to plant development. Key among them is photosynthesis, the process that plants use when converting sunlight to energy. Phosphorus is also important to respiration, cell enlargement, cell division, energy storage and energy transfer. For all these reasons, phosphorous is integral to the quality of the plant and the fruit it produces. P also moves easily from older plant tissue to new plant tissue. Farmers can often tell if their crops are deficient in phosphorus by examining the bottom (older) parts of the plant for signs of poor health.

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 either thermal-processed or acid-treated. The latter are considered to be more commercially important.

For more information on phosphorous as a primary nutrient, click here.

Phosphorus and Fertilizer Products

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.