Skip to content

Di-Ammonium Phosphate (DAP)

Di-Ammonium Phosphate (DAP) is the most widely used phosphatic fertiliser in India and the second largest fertiliser by volume after urea. The standard 18-46-0 grade supplies 18% nitrogen in ammoniacal form together with 46% phosphate as P2O5, of which more than 90% is water soluble. It is regulated under the Fertiliser Control Order (FCO) and falls within the Nutrient-Based Subsidy (NBS) regime administered by the Department of Fertilizers.

Composition

  • Grade: 18-46-0 (N-P2O5-K2O)
  • N form: 18% ammoniacal nitrogen
  • P form: 46% P2O5, more than 90% water soluble
  • Appearance: dark brown to black granules, free flowing

IFFCO is the largest domestic supplier, with significant production at the Paradip and Kandla units; imports supplement domestic output to meet national demand.

Mode of action

When DAP dissolves in soil moisture, it forms a transiently alkaline reaction zone of ammonium and phosphate ions around the granule. The ammonium is taken up directly or nitrified, while phosphate ions react with soil cations and become available to roots over several weeks. The alkaline dissolution makes DAP less suitable for highly alkaline calcareous soils, where Ssp Single Super Phosphate is preferred.

Target use and dose

DAP is applied almost exclusively as a basal dose at sowing or transplanting because phosphate is poorly mobile in soil and must be placed close to developing roots. It is the dominant P source in paddy, wheat, cotton, oilseeds and pulses. For paddy, see Paddy First Dose Fertilizer. Complex NPK fertilisers such as Complex 20 20 0 13 and 10-26-26 are alternatives when sulphur or potash co-application is desired.

Subsidy and regulation

DAP is sold at a controlled retail price under NBS, with per-tonne nutrient-based subsidy notified twice a year by the Department of Fertilizers. The product is FCO-notified; specifications cover minimum nutrient content, granule size and moisture.

See also: Urea, Muriate Of Potash, Ssp Single Super Phosphate, Complex 20 20 0 13, Complex Npk Grades.

References

  1. DAP 18-46-0 Product Specification. Indian Farmers Fertiliser Cooperative (IFFCO).
  2. Diammonium Phosphate. Mosaic Crop Nutrition Resource Library.