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PDFWAC 16-200-721

Slowly released plant nutrients.

(1) No fertilizer label shall bear a statement that connotes or implies that certain plant nutrients contained in a fertilizer are released slowly over a period of time, unless the nutrient or nutrients are identified and guaranteed.
(2) Types of products with slow release properties recognized are:
(a) Water insoluble (nitrogen products only), such as natural organics, ureaform materials, urea-formaldehyde products, IBDU, oxamide, etc.;
(b) Coated slow release, such as sulfur coated urea and other encapsulated soluble fertilizers;
(c) Occluded slow release, where fertilizers or fertilizer materials are mixed with waxes, resins, or other inert materials and formed into particles; and
(d) Products containing water soluble nitrogen such as ureaform materials, urea-formaldehyde products, methylenediurea (MDU), dimethylenetriurea (DMTU), dicyanodianide (DCD), etc.
(3) The terms "water insoluble," "coated slow release," "slow release," "controlled release," "slowly available water soluble," and "occluded slow release" are accepted as descriptive of the products listed in subsection (2) of this section; however the registrant can show a testing program substantiating the claim (testing under guidance of experiment station personnel or a recognized reputable researcher acceptable to the director). A laboratory procedure, acceptable to the director for evaluating the release characteristics of the product(s) shall also be provided by the registrant upon request.
(4) When the nitrogen is organic, it shall be established that if a label states the amount of organic nitrogen present in a phrase, such as "nitrogen in organic form equivalent to X% N," then the water insoluble nitrogen guarantee shall not be less than sixty percent of the nitrogen so designated. For example: If the total nitrogen guarantee for a fertilizer is ten percent and the label states "Nitrogen in organic form equivalent to 2.5% N" then the water insoluble nitrogen guarantee shall not be less than 1.5% (2.5% x 0.6 = 1.5%).
(5) When a slowly released nutrient is less than fifteen percent of the guarantee for either total nitrogen (N), available phosphoric acid (P2O5), or soluble potash (K2O), as appropriate, the label shall bear no reference to such designations.
(6) AOAC method 2.074 (13th Edition), or as designated in subsequent editions, shall be used to confirm the coated slow release and occluded slow release nutrients and others whose slow release characteristics depend on particle size. AOAC method 2.072 (13th Edition) or as designated in subsequent editions, shall be used to determine the water insoluble nitrogen of organic materials.
[Statutory Authority: Chapter 15.54 RCW. WSR 87-19-097 (Order 1952), ยง 16-200-721, filed 9/17/87.]
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