Section 73.3. Secondary plant nutrients

(a) A plant nutrient other than nitrogen, phosphorus and potassium, if mentioned in any form or manner, shall be registered and shall be guaranteed on the elemental basis. Sources of the elements guaranteed and proof of availability shall be submitted to the Secretary upon request.

(b) The minimum percentages of nutrients which will be accepted for registration are shown in the following table:

Element	Percent
Calcium (Ca)	1.00
Magnesium (Mg)	0.50
Sulfur (S)	1.00
Boron (B)	0.02
Chlorine (Cl)	0.10
Cobalt (Co)	0.0005
Copper (Cu)	0.05
Iron (Fe)	0.10
Manganese (Mn)	0.05
Molybdenum (Mo)	0.0005
Sodium (Na)	0.10
Zinc (Zn)	0.05

(c) The guarantee or claim for the plant nutrients listed in subsection (b) and immediately following the guarantees for the primary plant nutrients.

(e) A proposed label and direction for use of the fertilizer shall be furnished with the application for registration.

The provisions of this § 73.3 adopted July 28, 1972, effective July 29, 1972, 2 Pa.B. 1435.