ASSOCIATION OF AMERICAN PLANT FOOD CONTROL OFFICIALS (AAPFCO) OFFICIAL FERTILIZER DEFINITIONS 
PHOSPHATE PRODUCTS (P₂O₅)

 

P-10 — Acidulated Bone

Is ground bone or bone meal that has been treated with sulfuric acid.
(Official 1951)

P-3 — Ammoniated Superphosphate

Is a product obtained when superphosphate is treated with ammonia or with solutions which contain ammonia and other compounds of nitrogen. The guaranteed percentages of nitrogen and of available phosphate shall be stated as part of the name.
(Official 1993)

P-4 — Ammonium Phosphate (fertilizer quality)

Is a product obtained when phosphoric acid is treated with ammonia (anhydrous or aqueous) and consists principally of monoammonium phosphate and diammonium phosphate or a mixture of these two salts. The guaranteed percentage of nitrogen and of available phosphate shall be stated as part of the name.
(Official 1993)

P-5 — Ammonium Phosphate Sulfate (fertilizer quality)

Is a product obtained when a mixture of phosphoric acid and sulfuric acid is treated with ammonia. It consists principally of a mixture of ammonium phosphate and ammonium sulfate. The guaranteed percentages of nitrogen and Available Phosphate shall be stated as a part of the name.
(Official 1993)

P-29 — Ammonium Polyphosphate (fertilizer quality)

Is an ammonium salt of any of a series of polyphosphoric acids whose molecular structure contains two or more phosphorus atoms linked by oxygen. Solutions of ammonium polyphosphate may contain two or more of several phosphate species such as orthophosphates, pyrophosphates and linear phosphate species containing three or more phosphorus atoms which commonly include tripolyphosphates and tetrapolyphosphates. The guaranteed percentages of total nitrogen and available phosphate shall be stated as part of the brand name.
(Official 2002)

P-2 — Available Phosphate

Moved. See T-126.
(SA 2020)

P-6 — Basic Lime Phosphate (lime-superphosphate)

Is a superphosphate to which liming materials have been added in a quantity at least six percent (6%) calcium carbonate equivalent in excess of the quantity required to convert all water soluble phosphate to the citrate soluble form.
(Official 1951)

P-7 — Basic Phosphate Slag

Is a by-product obtained in the manufacture of steel from phosphatic iron ores. The product shall contain no admixture of materials other than those resulting from the original process of manufacture. It shall contain not less than twelve percent (12%) of total phosphate, of which at least eighty percent (80%) shall be available phosphate. It shall be ground so that not less than seventy percent (70%) of the material passes through a U.S. Standard No. 100 sieve (150 µm opening) and ninety percent (90%) passes through a U.S. Standard No. 50 sieve (300 µm opening). Any basic phosphate slag not conforming to this definition shall be designated low phosphate.
(Official 1993)

P-12 — Bone Meal

Is ground animal bones that have been previously steamed under pressure, heated, or rendered sterile in some other acceptable manner.
(Official 1997)

P-20 — Calcined Phosphate

Is phosphate rock which has been heated, with or without one or more catalysts or reagents, sufficient to volatilize and remove most or all organic, carbonate, fluoride and other impurities, and/or thermally altered to more available calcium phosphate compounds, depending on the process. A significant portion of the phosphate is citrate soluble and such percentage shall be stated as part of the brand name. Included are products known as fused tricalcium phosphate, defluorinated phosphate, rhenania phosphate and various trade names.
(Official 1994)

P-17 — Calcium Metaphosphate

Is a vitreous product substantially free from crystalline phosphates, resulting from the treatment of phosphate rock with gaseous phosphorus pentoxide at high temperatures. The guaranteed percentage of available phosphate shall be stated as part of the name.
(Official 1993)

P-8 — Citrate Soluble Phosphate

Is that part of the total phosphate in a fertilizer that is insoluble in water but soluble in a solution of citrate of ammonia according to the method adopted by the AOAC International.
(Official 1993)

P-21 — DAP (fertilizer quality)

Is a product composed of ammonium phosphates, principally diammonium phosphate, resulting from the ammoniation of phosphoric acid. It may contain up to 2% non-ammoniacal nitrogen. The guaranteed percentage of nitrogen and available phosphate shall be stated as part of the name. 
(Official 1993)

P-9 — Dicalcium Phosphate

Is a manufactured product consisting chiefly of dicalcic salt of phosphoric acid.
(Official 1951)

P-26 — Dipotassium Phosphate (dibasic potassium phosphate) (K₂HPO₄) (fertilizer quality)

Is the dipotassium salt of phosphoric acid. Pure dipotassium phosphate contains forty percent (40%) available phosphate and fifty-three percent (53%) soluble potash. The guaranteed percentages of available phosphate and soluble potash shall be stated as part of the brand name.
(Official 2002)

P-31 — Dried Whey Sludge (fertilizer quality)

Is a by-product removed at whey processing plants, which has been de-watered and dried. It shall contain not less than five percent (5%) total nitrogen, nine percent (9%) available phosphate, and one percent (1%) soluble potash.
(Official 2003)

P-11 — Ground Raw Bone

Is ground animal bones that have not been previously steamed under pressure, heated, or otherwise manipulated.
(Official 1984)

P-39 — Hydroxylapatite

Is a naturally-formed phosphate rock with the formula Ca₅(PO₄)₃(OH). The fluorine content is less than 1%.
(Tentative WA 2019; Official SA 2019)

P-23‡ — Magnesium Ammonium Phosphate

a. Is chiefly the ammonium and magnesium double salt of orthophosphoric acid and contains at least thirty percent (7%) nitrogen, thirteen percent (13%) magnesium and forty percent (40%) available phosphate. It is a source of slowly available nitrogen, magnesium, and available phosphate.
(Official 1995)
b. Hexahydrate is chiefly the ammonium and magnesium double salt of orthophosphoric acid and contains at least twelve percent (5%) nitrogen, ten percent (10%) magnesium and twenty- eight percent (28%) available phosphate. It is a source of slowly available nitrogen, magnesium and available phosphate.
(Official 2012)

P-24‡ — Magnesium Potassium Phosphate

Is chiefly the magnesium and potassium double salt of orthophosphoric acid and its condensates. It shall contain not less than twenty-one percent (21%) soluble potash, twelve percent (12%) magnesium and thirty-six percent (36%) available phosphate. It is a source of slowly available potash, magnesium and available phosphate.
(Official 1995)

P-22 — MAP (fertilizer quality)

Is a product composed of ammonium phosphates, principally monoammonium phosphate, resulting from the ammoniation of phosphoric acid. The guaranteed percentage of nitrogen and available phosphate shall be stated as part of the name.
(Official 1991)

P-25 — Monopotassium Phosphate (monobasic potassium phosphate) (KH₂PO₄) (fertilizer quality)

Is the monopotassium salt of phosphoric acid. Pure monopotassium phosphate contains fifty-two percent (52%) available phosphate and thirty-four percent (34%) soluble potash. The guaranteed percentages of available phosphate and soluble potash shall be stated as part of the brand name.
(Official 2002)

P-1 — Phosphate

Moved. See T-125.

P-13 — Phosphate Rock

Is a natural rock containing one or more calcium phosphate minerals of sufficient purity and quantity to permit its use, either directly or after concentration, in the manufacture of commercial products.
(Official 1952)

P-18 — Polyphosphates

Is a general term pertaining to salts of any of a series of polyphosphoric acids, whose molecular structure contain two or more phosphorus atoms linked by oxygen. Solutions may contain several species such as orthophosphates, pyrophosphates, and polyphosphates containing three (3) or more phosphorus atoms, commonly known as tripolyphosphates or tetrapolyphosphates and water.
(Official 1976)

P-28 — Potassium Polyphosphate (fertilizer quality)

Is a potassium salt of any of a series of polyphosphoric acids whose molecular structure contains two or more phosphorus atoms linked by oxygen. Solutions of potassium polyphosphate may contain two or more of several phosphate species such as orthophosphates, pyrophosphates and linear phosphate species containing three or more phosphorus atoms which commonly include tripolyphosphates and tetrapolyphosphates. The guaranteed percentages of available phosphate and soluble potash shall be stated as part of the brand name.
(Official 2002)

P-14 — Precipitated Phosphate

Is a product consisting mainly of dicalcium phosphate obtained by neutralizing with calcium hydroxide the acid solution of either phosphate rock or processed bone. 
(Official 1951)

P-16 — Soft Phosphate with Colloidal Clay

Is a very finely divided low-analysis by-product from mining Florida rock phosphate by a hydraulic process in which the colloidal materials settle at points in artificial ponds and basins farther from the washer, and are later removed after the natural evaporation of the water.
(Official 1951)

P-15 — Superphosphate

Is a product obtained when rock phosphate is treated with either sulfuric acid, phosphoric acid, or a mixture of these acids. The guaranteed percentage of available phosphate shall be stated as a part of the name. Other nutrients present above minimal levels may be guaranteed.
(Official 2006)

P-19 — Superphosphoric Acid

Is the acid form of polyphosphates, consisting of a mixture of orthophosphoric and polyphosphoric acids. Species distribution varies with concentration, typically sixty-eight to eighty-three percent (68–83%) P₂O₅.
(Official 1976)

P-27 — Tripotassium Phosphate (tribasic potassium phosphate) (K₃PO₄) (fertilizer quality)

Is the tripotassium salt of phosphoric acid. Pure tripotassium phosphate contains thirty-three percent (33%) available phosphate and sixty-six percent (66%) soluble potash. The guaranteed percentages of available phosphate and soluble potash shall be stated as part of the brand name.
(Official 2002)

P-30 — Urea Phosphate

Is the solid crystalline product formed by processing mixtures of urea and phosphoric acid. Typically the product contains eighteen percent (18%) urea nitrogen and forty-four percent (44%) available phosphate.
(Official 2002)

P-32 — Ammonium Metaphosphate

A high concentrate of nitrogen and phosphorus compound fertilizer. The formula is (NH₄)₃PO₄, which is unstable. The final product after the loss of ammonia is Diammonium Phosphate.
(Official 2013)

P-33 — Ammonium Phosphate-Nitrate

Is a mixture of ammonium nitrate and MAP (73% AN and 27% MAP) with grade of 27-14-0 or AN and DAP (70% AN and 30% DAP).
(Official 2013)

P-34 — Spent Bone Black

Contains approximately 10% carbon, 84% calcium phosphate and 6% calcium carbonate. It is made from charring of bones or waste ivory.
(Official 2013)

P-35 — Phosphatic Limestone

It contains approximately 23% of tri-calcium phosphate and 70% of calcium carbonate.
(Official 2013)

P-36 — Magnesium Phosphate

Is the magnesium salt of phosphoric acid, generally expressed as MgHPO₄ and its hydrated forms.
(Official 2013)

P-37 — Nitric Phosphate

These fertilizer products are manufactured from the reaction of nitric acid and phosphate rock.
(Official 2013)

P-38 — Superphosphate, Enriched

Is a mixture of single superphosphate and triple superphosphate, made by treating phosphate rock with both sulfuric acid and phosphoric acid.
(Official 2014)