(a) On and after the effective date of this amendatory Act of the 96th General Assembly, a unit of local government may not regulate fertilizer in a manner more restrictive than the regulation of fertilizer by the State under this Act, unless the Department of Agriculture determines that a proposed ordinance of a unit of local government is reasonable under the specific circumstances based on standards that the Department shall adopt by rule. This Section is a limitation under subsection (i) of Section 6 of Article VII of the Illinois Constitution on the concurrent exercise by home rule units of powers and functions exercised by the State.
     (b) Subsection (a) of this Section shall not apply to any local ordinance or regulation in effect before the effective date of this amendatory Act of the 96th General Assembly.