Neb. Rev. Stat. § 57-219

Oil and gas leases, issued pursuant hereto, shall be for terms not to exceed ten years and as long thereafter as oil or gas is produced in paying quantities. Such leases shall provide for annual delay rentals of not less than twenty-five cents per acre and for a royalty of not less than twelve and one-half percent of all oil, gas, hydrocarbons and all other petroleum products produced and saved from the lands covered thereby and not used in the development and operation of the leased premises, or twelve and one-half percent of the market value thereof at the leased premises, free of cost to the lessor.