RSA 431:4-d: Preemption of Local Regulation.

Except as otherwise specifically provided in this subdivision, no ordinance or regulation of local government, including but not limited to, an action by a local governmental agency or department, a county board of commissioners or a city council, or a local regulation adopted by the use of an initiative measure, may prohibit or in any way attempt to regulate any matter relating to the registration, sale, formulation, or transportation of fertilizer. Additionally, no local regulation shall regulate the type of fertilizer when used for agricultural purposes as defined by RSA 21:34-a.