Diammonium Phosphate (DAP) Fertilizer: The 18-46-0 Label and When to Use It
Decision details
Fits if: Growers and wholesalers comparing straight phosphate classes (DAP vs TSP vs MAP vs rock phosphate) by declared analysis at a Malaysian shop.
Main drawback: No potassium and no calcium or sulphur credit; DAP is a P-plus-N input, not a complete fertilizer.
Compare: declared N and P2O5 on the bag; cost per kg of declared P2O5 at the same pack size; placement method; the crop programme you follow; what the shop actually stocks.
In this guide
Summary: DAP is the world’s most-used straight phosphate fertilizer. Its cited composition is 18% N and 46% P2O5 (20% P), grade 18-46-0 [source]. This page explains what those figures mean, how DAP compares with the phosphate classes Malaysian official programmes actually name, and which buyer it fits.
What diammonium phosphate is
DAP is made by reacting ammonia with phosphoric acid; the result is a granular, highly water-soluble fertilizer. The manufacturer resource page cited here states: composition 18% N and 46% P2O5 (20% P), standard nutrient grade 18-46-0, chemical formula (NH4)2HPO4 [source].
Read the numbers the way you would read any bag label:
- The figures are percentages by mass: for every kg of product, the declared nitrogen and phosphate follow from the cited composition of 18% N and 46% P2O5 [source].
- The N-P-K third figure is zero: DAP carries no potassium.
- The analysis above is one manufacturer’s standard-grade statement (era 2026-10-21); the bag in front of you at the shop is the authority for what you are buying.
What it does, and at which crop stage
Phosphate is the nutrient of early establishment — root growth and energy transfer — which is why straight phosphate classes are placed at or before planting, in or near the planting row, rather than broadcast late. DAP’s nitrogen half adds a starter-N effect in the same granule. That makes DAP a basal-placement input, not a top dressing.
The Malaysian official programmes cited on this site fill their phosphate slots differently: the banana programme uses rock phosphate (CIRP) and TSP in the planting-hole mix [source], the tongkat ali package uses TSP in the base-hole dressing [source], and the rice programme lists MAP (11% N, 52% P2O5) as an option alongside MOP [source]. Those classes — not DAP — are the ones with programme-written rates here. If you substitute DAP for one of them, you are changing the analysis and the arithmetic of the rate.
The name at the shop, and the BM bridge
The Malaysian search demand for DAP is in English — estate assistants, wholesalers and vegetable growers search the chemical name or the abbreviation. At the shop, “DAP” is the counter name; verify the bag states 18-46-0 before paying, because TSP bags sit on the same shelf with a similar-looking 0-46-0 grade and no nitrogen [source].
Malay-speaking home growers usually ask by effect — baja untuk akar, baja untuk buah, baja permulaan — rather than by chemical class. Those effect questions have BM owners on this site: cara baca label NPK and NPK 15-15-15. This English page answers the chemistry question and hands back to those owners.
DAP vs the adjacent phosphate classes
| Class | Declared analysis (source) | N contribution | Solubility and speed | Who it fits |
|---|---|---|---|---|
| Diammonium phosphate (DAP) | 18% N, 46% P2O5 (20% P), grade 18-46-0 [source] | Yes — starter N in the same granule | Highly water-soluble; phosphate available early in the season | Buyers wanting P plus some N in one basal granule |
| Triple super phosphate (TSP) | Grade 0-46-0 as observed on a Malaysian listing [source] | None | Water-soluble phosphate, no N credit | Programmes naming TSP; buyers who already handle N separately — local price owner linked below |
| Monoammonium phosphate (MAP) | 11% N, 52% P2O5, listed as a rice-programme option [source] | Yes — smaller share than DAP | Water-soluble | Rice programmes that name MAP; slightly different N-to-P arithmetic |
| Rock phosphate (CIRP) | Named as the planting-hole phosphate in the banana programme [source] | None | Slow-release; solubility depends on soil acidity | Programmes naming CIRP; acidic-soil slow-P strategy |
| Compound NPK 15:15:15 | 15:15:15 named in the banana programme [source] | Yes, with K in the same bag | Depends on formulation | Buyers who want P, N and K together; see the NPK 15-15-15 guide |
The comparison is by declared analysis, not performance claims. Two straight phosphate bags with the same P2O5 scale behave differently in soil when one carries ammonium and the other does not.
Handling and storage, stated factually
- Keep bags sealed and dry; soluble phosphate granules cake and dust when damp.
- DAP is not a hazardous-class fertilizer in ordinary retail handling; follow the product’s safety data sheet for the bag you buy.
- Do not mix DAP freely with strongly alkaline materials in the same blend; as a general chemistry principle, ammonia can be released when ammonium phosphates meet strong alkalis. Store and blend per the product sheet.
- Wash hands after handling; keep bags away from children and livestock. No medical or fear claims are made or needed.
The pick — and who should not take it
For the buyer standing in front of straight phosphate bags: match the class to your programme first. If your programme names TSP, MAP or CIRP, that is the class to ask for [source]. Choose DAP when you want soluble phosphate and a starter nitrogen contribution in one granule and the per-kg-of-P2O5 arithmetic works out at your counter. Do not choose DAP if you need potassium or calcium-sulphur credit in the same application — it carries none [source].
Where to go next
- The phosphate class with a Malaysian price owner: harga baja TSP
- The compound comparison page: NPK 15-15-15 explained
- How to read any NPK label: cara baca NPK pada label
- The nitrogen straight class: calcium ammonium nitrate
Frequently asked questions
What is diammonium phosphate fertilizer used for?
As a basal phosphate source at or before planting, placed where young roots reach it. Its composition is 18% N and 46% P2O5 (20% P), standard grade 18-46-0 [source]. Phosphate supports early root and shoot growth; this page admits no crop-specific rate — the product label and your crop programme decide rate and placement.
DAP vs TSP — what is the difference?
Both are straight phosphate classes. A TSP listing observed in Malaysia carries the grade 0-46-0 — phosphate only, no nitrogen [source]. DAP declares 18% N and 46% P2O5 (20% P) in the same granule [source]. Same P2O5 scale on paper; DAP adds nitrogen and shifts the price comparison — compare cost per kg of declared P2O5, not per bag.
Is DAP suitable for oil palm, durian and vegetables?
No crop-specific DAP rate is admitted here. The Malaysian programmes cited on this page use other classes in their phosphate slots — rock phosphate (CIRP) and TSP in the banana programme [source], and MAP as a rice option [source]. If your programme names one of those, that is the class your rates were written for.
Does DAP make soil acidic?
Around a DAP granule the initial reaction is alkaline, then the ammonium nitrogen converts in soil and contributes to the same gradual acidification as other ammonium-bearing fertilizers. This is textbook chemistry framing, not a measured claim about your field; a soil test decides whether lime is needed.
How do I ask for DAP at a Malaysian shop?
The counter name is DAP; bring the full name diammonium phosphate and check the declared analysis figures 18% N and 46% P2O5 against the bag you are handed. Malaysian official programmes quoted here name TSP, MAP and CIRP rather than DAP [source], so the label, not a schedule slot, identifies the product.