Analysis
HTS 3105.30.00 covers diammonium hydrogenorthophosphate (Diammonium phosphate) under heading 3105 (mineral or chemical fertilizers containing two or three of the fertilizing elements…).
The normal trade relations rate here is zero, shared by about 100% of the 24 tariff lines in chapter 31, a useful check when a neighbouring dutiable line is a candidate. Duty-free at the general rate does not rule out additional duties under Chapter 99, such as Section 301 or Section 232 measures, which depend on the country of origin.
Census statistics map these goods to NAICS 325312 (Phosphatic Fertilizer Manufacturing), an industry of 79 US establishments employing 6,248 people. That concordance is how imports of this line are compared with US output.
All 7 neighbouring lines carry the same duty-free rate, so a borderline choice between them changes the statistics reported, not the duty paid.
Every edition we compared, from Jan 2023 to Oct 2026 (Rev. 22), shows the same general rate of Free.
Neighbouring lines
| Line | Description | General rate |
|---|---|---|
| 3105.10.00 | Products of this chapter in tablets or similar forms or in packages of a gross weight not exceeding 10 kg | Free |
| 3105.20.00 | Mineral or chemical fertilizers containing the three fertilizing elements nitrogen, phosphorus and potassium | Free |
| 3105.40.00 | Ammonium dihydrogenorthophosphate (Monoammonium phosphate) and mixtures thereof with diammonium hydrogenorthophosphate (Diammonium phosphate) | Free |
| 3105.51.00 | Containing nitrates and phosphates | Free |
| 3105.59.00 | Other mineral or chemical fertilizers containing the two fertilizing elements nitrogen and phosphorus: other | Free |
| 3105.60.00 | Mineral or chemical fertilizers containing the two fertilizing elements phosphorus and potassium | Free |
| 3105.90.00 | Mineral or chemical fertilizers containing two or three of the fertilizing elements nitrogen, phosphorus and potassium; other fertilizers; goods of this chapter in tablets or similar forms or in packages of a gross weight not exceeding 10 kg: other | Free |