Wash. Admin. Code § 16-200-708
(2) It is unlawful to distribute a commercial fertilizer in Washington that exceeds the standards for nonnutritive substances established in RCW 15.54.800(3). The department will determine if a commercial fertilizer exceeds the standards by using the maximum application rates and by either:
[Statutory Authority: Chapter 15.54 RCW. WSR 99-02-035, § 16-200-708, filed 12/30/98, effective 1/30/99. Statutory Authority: RCW 15.54.800. WSR 91-01-015 (Order 2066), § 16-200-708, filed 12/7/90, effective 1/7/91.]