When the commissioner finds, after public hearing following due notice, 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, the commissioner 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, that the effective date of such regulation shall be not less than six (6) months following the issuance of the regulation; and provided further, that for a period of two (2) years following the effective date of the regulation, the equivalent of calcium and magnesium may also be shown in the form of calcium oxide and magnesium oxide and/or calcium carbonate and magnesium carbonate.