NPS [CAS?]-13S combines the balanced one-to-one nitrogen and phosphorus ratio of [CAS?] with a declared 13 % sulfur component. Total declared nutrient reaches 53 %, which makes it one of the more concentrated zero-potassium compounds in general trade. It is specified where a cereal or oilseed program needs a substantial basal charge of both nitrogen and phosphorus and where sulfur has become limiting — a combination that has become progressively more common as sulfur deficiency has spread into soils that historically did not require it.
Substance identity
| Field | Value |
|---|---|
| Product type | Formulation — no single CAS number |
| Grade | [CAS?]-13S (N — P₂O₅ — K₂O — S) |
| Nutrients per tonne | 200 kg N · 200 kg P₂O₅ · 0 kg K₂O · 130 kg S |
| Total declared nutrient | 53 % |
| Sulfur expressed as SO₃ | 13 % S = 32.5 % SO₃ |
| Typical constituents | ammonium phosphates with ammonium sulfate, sometimes urea |
No single CAS number applies to a formulation. Constituent substances hold their own registry numbers and are declared individually on the safety data sheet.
Specification
Typical commercial declaration — confirm on certificate of analysis:
| Parameter | Typical |
|---|---|
| Total nitrogen (N) | 20 % |
| P₂O₅, total | 20 % |
| K₂O | 0 % |
| Sulfur (S) | 13 % |
| Sulfur form | sulfate — confirm on specification |
| Moisture | ≤ 1.5 – 2.5 % |
| Particle size | ≥ 90 % within 2 – 4 mm |
| Appearance | granular |
Properties
-
53 % total declared nutrient, against 49 % for NPS [CAS?]-13S and 40 % for NP [CAS?]. Every additional point of declared nutrient displaces a point of carrier, filler and moisture that still has to be freighted, stored and spread.
-
N : S ratio of about 1.5 : 1 in the product. Crop nitrogen-to-sulfur uptake ratios are commonly in the range of roughly 7 : 1 to 15 : 1 for cereals and are appreciably narrower for brassicas. A product ratio of 1.5 : 1 therefore supplies sulfur well ahead of the crop’s proportional need relative to nitrogen — which is exactly the intent when a soil is sulfur-depleted and the reserve has to be rebuilt, but it also means the balance of the season’s nitrogen must come from a separate, sulfur-free source. This grade is a basal product, not a whole-season nitrogen program.
- Sulfate mobility. Sulfate sulfur leaches on sandy soils under high rainfall or heavy irrigation. On such soils, applying the full sulfur requirement far ahead of demand is a loss risk.
- Sulfur form must be confirmed. Sulfate is immediately available; elemental sulfur requires microbial oxidation before the crop can take it up. Both declare as “13 % S”.
- Nitrogen form — ammoniacal versus ureic — is not visible in the grade and should be requested.
Applications
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Basal fertilizer for cereals on sulfur-deficient soils — wheat, maize, barley, sorghum — drilled or broadcast and incorporated at or before sowing.
-
Oilseeds and pulses where the balanced NP ratio suits the soil test and a high sulfur input is required.
- Where this grade beats [CAS?]-13S. When the same phosphorus and sulfur are wanted but with 25 % more basal nitrogen — cool early-season soils with slow mineralization, high-demand crops, or programs deliberately consolidating nitrogen into fewer field passes.
- Where [CAS?]-13S is preferable instead. When basal nitrogen is deliberately restricted: to limit early lodging risk in cereals, to avoid excessive vegetative growth, or where the nitrogen program is built around split topdressings timed to crop stage. Choosing between them is a decision about when nitrogen arrives, not about how much phosphorus or sulfur is applied.
- The 0 % K decision stands as for all zero-potassium compounds: justified by soil test, crop removal, or separate potassium supply — and not sustainable indefinitely on soils of moderate or low potassium status.
Handling and storage
Dry, covered, ventilated storage; bagged on pallets, clear of floors and walls; humidity control. Multi-salt compounds have a lower critical relative humidity than any of their components, and where urea is among the constituents that threshold falls further — these products cake readily in humid conditions. Limit stack height. Segregate strictly from lime, basic slag and other alkaline materials. Keep away from heat and from moisture ingress. Minimize handling transfers to limit fines.
Notes
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No single CAS number; constituents individually on the SDS.
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13 % S = 32.5 % SO₃. Confirm the declaration basis before any comparison.
- Confirm the form of both the sulfur and the nitrogen; the grade alone does not carry that information.
- Conversions: 20 % P₂O₅ = 8.7 % elemental P; 13 % S = 130 kg S per tonne.