(1) Water insoluble (N products only), such as natural organics, urea formaldehyde, isobutylidene diurea and oxamide.

(2) Coated slow release such as sulfur coated urea and other encapsulated soluble fertilizers.

(3) Products containing water soluble nitrogen such as ureaform materials, urea formaldehyde products, methylenediurea (MDU), dimethylene triurea (DMTU), dicyanodiamide (DCD).

(4) Occluded slow release, where fertilizers or fertilizer materials are mixed with waxes, resins, or other inert materials and formed into particles.

The terms “water insoluble,” “coated slow release,” “slowly available water soluble” and “occluded slow release” are accepted as descriptive of these products provided the claim is substantiated by a research study as required by section 2300(b).

(5) Products containing phosphorous acid such as potassium phosphite and ammonium phosphite which undergo a degree of conversion in plants or soils to available phosphoric acid (P₂O₅).

(6) Effective January 1, 2006, products containing elemental sulfur are a source of nutrient sulfur when applied to soil. Other application techniques for elemental sulfur must be substantiated by scientific research as required by Section 2300(b) that demonstrates availability of an efficacious amount of nutrient sulfur for plant uptake generally consistent with soil application.