NP [CAS?] is a compound fertilizer supplying nitrogen and phosphorus in a phosphorus-leaning ratio, with no potassium. It is a basal and starter product, widely used in rice, maize and vegetable systems on soils that already test adequate in exchangeable potassium. The grade has a long history in South and Southeast Asian cropping, where it is often the standard planting fertilizer. Understanding what it is — and equally what it is not — starts with the fact that it is a manufactured formulation rather than a chemical substance.
Substance identity
| Field | Value |
|---|---|
| Product type | Formulation — no single CAS number |
| Grade | [CAS?] (N — P₂O₅ — K₂O) |
| Nutrients per tonne | 160 kg N · 200 kg P₂O₅ · 0 kg K₂O |
| Typical constituents | ammonium phosphates and ammonium sulfate; route varies by manufacturer |
This product has no CAS number and cannot have one. CAS Registry Numbers identify chemical substances. [CAS?] is a blend or co-granulate of several substances, each of which has its own identifier — monoammonium phosphate is CAS 7722-76-1, diammonium phosphate is CAS 7783-28-0, ammonium sulfate and urea carry theirs. Any supplier or document presenting a single CAS number for a compound NPK grade is misapplying the registry. The constituents should be listed individually on the safety data sheet.
Specification
Typical commercial declaration — confirm on certificate of analysis:
| Parameter | Typical |
|---|---|
| Total nitrogen (N) | 16 % |
| P₂O₅, total | 20 % |
| Water-soluble P₂O₅ as % of total | declare on CoA |
| K₂O | 0 % |
| Sulfur (S) | route-dependent — see notes; not guaranteed unless declared |
| Moisture | ≤ 1.5 – 2.5 % |
| Particle size | ≥ 90 % within 2 – 4 mm |
| Appearance | granular, color varies by manufacturing route |
Properties
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N : P₂O₅ ratio of 0.8 : 1 — phosphorus-dominant. This is a genuinely different agronomic tool from a balanced 1 : 1 grade, and the two are not interchangeable at equal rates.
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Nitrogen form matters and should be asked about. Nitrogen supplied as ammonium behaves differently from nitrogen supplied as urea: ammonium is held on the exchange complex and is less prone to early leaching loss, whereas urea must hydrolyse first and is subject to volatilization loss if left on a warm, moist, high-pH soil surface without incorporation. The declared total N does not distinguish the two. Request the form.
- Compound versus blend. In a true compound, every granule contains every nutrient, so nutrients cannot segregate in transport or spreading. In a physical blend, each granule contains one component, and segregation by particle size is a real field risk. Which one a given “[CAS?]” is should be confirmed.
- Uniform granulometry allows predictable spreading across the boom width.
Applications
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Basal and starter application at planting in rice, maize, wheat and vegetables — front-loading phosphorus, which the crop needs earliest and which moves least in the soil, together with a moderate nitrogen charge.
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Why a P-leaning ratio at planting. Phosphorus uptake is diffusion-limited and root-interception-dependent, so the whole seasonal P requirement is normally applied before or at sowing. Nitrogen, by contrast, is mobile, subject to loss, and needed in the largest quantity during rapid vegetative growth well after establishment. A 0.8 : 1 basal grade therefore covers the full P need while deliberately supplying only the starter fraction of N, with the remainder applied as split topdressings of urea or another straight N source.
- The 0 % K decision. Appropriate where soil testing shows adequate or high exchangeable potassium, where the crop’s K removal is low, or where K is supplied separately as potassium chloride or sulfate. It is not appropriate as a permanent program on soils of moderate or low K status: continuous use of zero-K compounds mines soil potassium, and the deficiency that eventually appears is expensive to correct and usually shows up first as reduced grain fill or lodging rather than as an obvious foliar symptom. Base the decision on a soil test.
- Rice systems in particular, where much of the crop’s potassium requirement can be met from irrigation water, soil reserves and returned straw.
Handling and storage
Store dry, covered and ventilated, bagged on pallets, clear of walls and floors. Compound fertilizers containing multiple salts generally have a lower critical relative humidity than any of their individual components, so humidity control matters more here than for a straight product. Limit stack height to prevent set. Keep away from lime, basic slag and other alkaline materials, which liberate ammonia from ammonium-containing products. Avoid heat and moisture ingress. Minimize handling transfers to limit fines.
Notes
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No single CAS number exists for this product; constituents are listed separately on the SDS.
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Sulfur: grades of this analysis are frequently produced by an ammonium-phosphate-sulfate route, in which case the product carries substantial incidental sulfur. Where S is not part of the declared grade it is not guaranteed, may vary lot to lot, and must not be relied on agronomically. If sulfur is required, specify a declared NPS grade — see NPS [CAS?]-13.
- Conversion: 20 % P₂O₅ = 8.7 % elemental P.