| TEST ITEMS | TEST STANDARD I | TEST STANDARD II |
|---|---|---|
| N/% ≧ | 20.5 | 19 |
| S/% ≧ | 24 | 21 |
| H₂SO₄/% ≦ | 0.05 | 0.2 |
| H₂O/% ≦ | 0.5 | 2 |
| Water insoluble matter/% ≦ | 0.5 | 2 |
| CL-/% ≦ | 1 | 2 |
Growers apply ammonium sulfate where supplemental nitrogen and sulfur are needed to meet plant nutritional requirements. While other nitrogen sources may be more concentrated and economical, ammonium sulfate provides an excellent sulfur source essential for numerous plant functions including protein synthesis.
The ammonium form makes it particularly suitable for flooded rice fields where nitrate-based fertilizers would be lost to denitrification.
Ammonium sulfate solutions are often added to post-emergence herbicide sprays to improve weed control effectiveness, especially in water containing calcium, magnesium, or sodium. High-purity grades are recommended to prevent spray nozzle clogging.