The board shall, if the foregoing proceedings appear to be regular, issue to the applicant a lease on the land. Each lease shall contain a covenant or provision (1) that the Board of Educational Lands and Funds may, whenever such board deems it to be for the best interest of the state, adjust the rental of such lands; (2) that the lessee will not sublease or otherwise dispose of such lands without the written consent of the board and will commit no waste or damage on the land nor permit others to do so; (3) that the lessee will observe and carry out soil conservation requirements according to the rules and regulations of the board; (4) that the lessee will pay for the use of such lands the fair market rental as determined by the board; (5) that, upon a failure to pay any rental for a period of six months from the time the payment becomes due or upon failure to perform any of the covenants of the lease, the lease may be forfeited and fully set aside, as provided for in sections 72-235 to 72-239; (6) that the lessee will promptly pay the rental semiannually in advance; (7) that in the event the lessee shall fail to pay rental in advance by the due date, interest shall be assessed at an annual interest rate of nine percent until such time as the rent is paid; and (8) that the premises will be surrendered at the expiration of the lease, unless renewed, or upon violation of any of the terms of the lease. Leases shall be for periods of five to twelve years less the period intervening between the date of the execution of the lease and December 31 of the previous year. The board may offer a lease for a period of less than five years if a lease failed to generate interest at an auction and if the board agrees that reducing the minimum lease term will attract a bid or bids for such a lease. When two or more contiguous tracts are under separate lease with different expiration dates, the board may, if it is deemed to be in the best interest of the state, offer leases for less than twelve years on tracts having the earlier lease expiration date, to coincide with the last expiring lease, in order that all contiguous lands eventually may be offered under one lease.