ASSOCIATION OF AMERICAN PLANT FOOD CONTROL OFFICIALS (AAPFCO) OFFICIAL FERTILIZER DEFINITIONS
SULFUR (S) PRODUCTS

S-2 — Ammonium Sulfate Nitrate

See N-8.

S-8 — Ammonium Thiosulfate

See N-37.
(Official 1990)

S-10 — Calcium Thiosulfate

See Ca-19.
(Official 1999)

S-11 — Dimethyl Sulfone (DMS)

Is a sulfur compound that has the formula C₂H₆SO₂.
(Official 2004)

S-4 — Double Sulfate of Potash and Magnesium

See K-9.

S-6 — Gypsum

See Ca-15.

S-7 — Magnesium Sulfate

See Mg-4.

S-12 — Magnesium Thiosulfate (fertilizer quality)

Is a product composed principally of MgS₂O₃·2H₂O. It is commercially available in granular form and in aqueous solution. The guaranteed percentage of magnesium and sulfur shall be stated as part of the brand name.
(Official 2005)

S-9 — Potassium Thiosulfate

See K-12.
(Official 1999)

S-1 — Sulfate of Ammonia

See N-7.

S-5 — Sulfate of Potash

See K-10.

S-3 — Sulfate of Potash-Magnesia

See K-8.

S-13# — Sulfur (S)

Free sulfur (S°) in its elemental form. Sulfur particles that are less than 100μ can oxidize over time and are a source of slow-release sulfur. If slow-release sulfur is claimed, only the portion that is less than 100μ would be considered slow release.
(Tentative WA 2019, Official SA 2019)

Secretary’s Note: S-8 Manganese Sulfate and M-1 Manganese (II) Sulfate in Official Publication No. 54 were deleted and the “S” definitions renumbered.
(Official 2001)