Di-ammonium Phosphate popularly known as DAP is a preferred fertilizer in India
because it contains both Nitrogen and Phosphorus which are primary macro-nutrients and part of
18 essential plant nutrients.
Di-ammonium Phosphate popularly known as DAP is a preferred fertilizer
in India because it contains both Nitrogen and Phosphorus which are primary macro-nutrients
and part of 18 essential plant nutrients.
DAP (NH4)2HPO4: Fertilizer grade DAP
Contains 18% Nitrogen and 46% Phosphorus (P2O5).. DAP is manufactured by reacting Ammonia
with Phosphoric acid under controlled conditions in fertilizer plants.
Soil Testing: For efficient use of this
fertilizer, soil must be tested for nitrogen and phosphorus content in order to
determine the required amount of DAP.
Basal Dose: DAP is the best suited fertilizer for
basal dose as through this we can apply full dose of phosphorus and one-third to half
dose of nitrogen. Remaining dosage of nitrogen can be applied through splits of urea at
other stages of crop . So DAP gives the best combination with urea fertilizer. DAP is
also the best fertilizer for pulses where less nitrogen and higher phosphorus is needed
as starter dose.
Placement of DAP: Since phosphorus is immobile in
soil, its source (DAP) should be placed at a distance where plant roots can easily
reach. Improper application of DAP may cause seedling injury due to release of ammonia.
DAP should be placed below seed, slightly to one side.
Soil Amendments: Nitrogen as well as phosphorus, give
best results in neutral soils. But in case of alkaline, volatilization losses of ammonia
are higher. So nitrogen use efficiency is reduced. Similarly excessive presence of
calcium in alkaline soils, makes complexes with phosphorus and ultimately results in
poor phosphorus recovery. So bringing soil pH to neutral by adding gypsum and leaching
can only improve N and P use efficiency of DAP.
In acidic soils, problem ions like Fe, AI and Mn become more active and form complexes
with phosphorus. Again P use efficiency is reduced. Nitrogen use is not affected much by
acidity. Addition of lime (CaCo3) to acidic soils brings soil pH to neutral. Thus P use
efficiency is improved.
It is a very popular fertilizer because of its excellent physical
properties and nutrient content. It is free flowing, dust-free and does not normally give
any storage problem. DAP is almost water-soluble and ultimately leaves acid effect on soils
because of ammonia (NH4) it contains. DAP on incorporation into soil, reacts with water and
gets converted into HPO4 and NH4. Ammonium (NH4) follows the same routes as in case of urea.
Phosphorus in DAP is present in best available from (HPO4). Depending upon the soil reaction
(pH), phosphorus exists in 3 forms which can be absorbed by plant roots. These are HPO4,
H2PO4 and PO4. Phosphorus, which is immobile in soil, is not subjected to leaching losses.
FCO Specifications
Parameter(By
weight)
%
Moisture
2.5 (Max)
Total Nitrogen
18.0 (Min)
Ammonical nitrogen
15.5 (Min)
Total nitrogen as urea
2.5 (Max)
P2O5
46.0 (Min)
Water soluble(P2O5)
41.0 (Min)
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