Diammonium phosphate

DAP is produced by fully neutralising phosphoric acid with ammonia gas, yielding a granular salt with a guaranteed analysis of roughly 18% nitrogen and 46% phosphorus. It is one of the world’s most widely produced and traded fertilizers.

Chemical formula

(NH₄)₂HPO₄

Nitrogen content

About 18% total nitrogen, as ammonium

Phosphorus content

About 46% P₂O₅, highly water-soluble

Granule reaction

Locally alkaline as the granule dissolves, then neutralises

DAP supplies phosphorus as its dominant nutrient in a highly water-soluble form, together with a substantial secondary contribution of nitrogen as ammonium, both released together as the granule dissolves.

• Phosphorus is supplied at high concentration and full water solubility
• Nitrogen is supplied as ammonium and nitrifies over time
• No potassium or micronutrients are supplied

DAP is used across cereal, oilseed, and many other cropping systems worldwide, often as a base phosphorus source in blended or compound fertilizer programs, and in some systems as a starter fertilizer.

• High analysis reduces bulk and handling cost per unit of nutrient
• Full water solubility supports rapid nutrient release once applied
• Common base material for compound NPK fertilizers

Because phosphorus moves little through most soils, DAP is generally most effective when placed where developing roots can access it. Some care is taken to avoid placing DAP in direct contact with germinating seed at high rates, since the temporary alkaline reaction and ammonia release near the granule can affect sensitive seedlings.

As with other phosphate fertilizers, the principal environmental concern is phosphorus movement to surface water, mainly through erosion and runoff of phosphorus-enriched soil, which can contribute to eutrophication.