(6) When the commissioner determines that the requirement for expressing the calcium and magnesium in elemental form would not impose an economic hardship on distributors and users of agricultural liming materials by reason of conflicting label requirements among the states, he may require by regulation thereafter that the minimum percentage of calcium oxide and magnesium oxide and/or calcium carbonate and magnesium carbonate shall be expressed in the following form: Total Calcium (Ca) .................... ____________________ percent
Total Magnesium (Mg) .................... ____________________ percent
Provided, however, that the effective date of said regulation shall be not less than six (6) months following the issuance thereof.