(1) To determine whether a commercial fertilizer meets Washington standards for metals, the department will use the following formula:
Pounds of product applied per acre per year X metal content of product (ppm)
1,000,000
The number used for pounds of product applied per acre per year will be the maximum application rate allowed by the commercial fertilizer label. If specific label directions for use are not available, the department will use the Washington application rates listed in subsection (2) of this section, divided by four.
(2) Using normal agronomic rates that are representative of soil, crop rotation, and climatic conditions in Washington state, the department developed the following Washington application rates:
Nutrient | 4 Yr. Cumulative Total (lbs./acre) |
Nitrogen (N) | 1600 |
Phosphorous (as P2O5) | 700 |
Potassium (as K2O) | 1600 |
Boron (B) | 12 |
Calcium (Ca) | 800 |
Chlorine (Cl) | 300 |
Copper (Cu) | 10 |
Iron (Fe) | 80 |
Magnesium (Mg) | 400 |
Manganese (Mn) | 40 |
Molybdenum (Mo) | 4 |
Sulfur (S) | 400 |
Zinc (Zn) | 30 |
Lime (CaCO3 equivalent) | 20,000 |
Gypsum (CaSO4) | 16,000 |
(3) To ensure that the maximum acceptable cumulative metals additions to soil are not exceeded, the department will assume the commercial fertilizer will be applied at the maximum rate as stated on the label or established in this rule.
[Statutory Authority: Chapter
15.54 RCW. WSR 99-02-035, § 16-200-7063, filed 12/30/98, effective 1/30/99.]