It is the intent of the legislative assembly of the state of North Dakota to exercise the legitimate police power of the state in order to protect the economic welfare of the citizens who rely for their livelihood on agricultural production and thereby protect the agricultural economic base of the state. It is in the public interest that certain of the terms and conditions of the leases of coal in place be regulated. The provisions of this chapter apply to all leases for the mining of coal entered into after April 9, 1975.