DAP (Di-Ammonium Phosphate, 18-46-0)
The phosphorus fertiliser for sowing. Get it near the seed at planting, credit the nitrogen it brings, and it earns its keep.
- Composition
- 18% N, 46% P₂O₅
- Form
- Grey-brown granules
- Subsidised price
- ~₹1,350 per 50 kg bag (2024–25)
- Best for
- At sowing — basal, near the seed
Overview
DAP supplies 46% phosphorus (as P₂O₅) and 18% nitrogen — the highest-analysis phosphatic fertiliser in common use, which is why a single bag covers a lot of ground. Phosphorus builds roots and drives early establishment, flowering and grain formation.
Phosphorus barely moves in soil, so placement is everything: DAP has to be put where the roots will grow, at sowing, in the seed furrow. Top-dressing DAP onto a standing crop later in the season is mostly wasted money — that is a job for a foliar spray, not DAP.
What it is and when to reach for it
- A concentrated phosphorus source with a useful shot of starter nitrogen — the standard basal fertiliser for most crops.
- Because it also carries 18% nitrogen, credit that against your urea plan or you will over-apply nitrogen by roughly a fifth.
- If your crop needs sulphur (oilseeds, pulses) or calcium, SSP is often the better phosphorus choice even though it is weaker — see SSP.
How to apply it well
- Apply the full phosphorus dose at sowing as basal — place it in the furrow, about 2–3 cm below and to the side of the seed.
- Band placement near the root zone beats broadcasting, because phosphorus fixed away from the roots is phosphorus wasted.
- On phosphorus-fixing acidic or high-calcium soils, banding matters even more — spread out, much of it locks up before roots reach it.
Common mistakes
- Top-dressing DAP on a standing crop — phosphorus will not travel down to the roots, so it mostly sits unused.
- Forgetting the 18% nitrogen it supplies and then applying a full separate nitrogen dose on top.
- Mixing DAP with urea and storing it — the two react and cake into a hard lump.
Organic alternative
Bone meal / rock phosphate
Bone meal and rock phosphate are slow-release phosphorus sources for organic systems — apply well before the crop needs it, near the root zone.
Crops it is used on
Open a crop for its full nutrient schedule.
Common questions
What does 18-46-0 mean on a DAP bag?
It is the N-P-K grade: 18% nitrogen, 46% phosphorus (as P₂O₅) and 0% potassium. So a 50 kg bag of DAP carries 9 kg of nitrogen and 23 kg of phosphorus.
Can I use DAP as a top dressing?
No — it is a poor top dressing. Phosphorus does not move in the soil, so DAP scattered on a standing crop never reaches the roots. Apply DAP at sowing, near the seed; for a mid-season boost use a foliar NPK spray instead.
DAP or SSP — which is better?
DAP is more concentrated (46% P vs 16%) so you carry fewer bags. But SSP also supplies sulphur and calcium, which oilseeds and pulses need — for mustard, groundnut or soybean, SSP (with urea to match the nitrogen) is often the better-value phosphorus source.
Composition and doses follow ICAR / Soil Health Card guidance; prices are the notified subsidised rates for the season shown and are guidance, not a quote. A soil test for your field always beats a general rate. See our editorial policy.