77-6-504. Lease rentals for part year. Lease rentals for agricultural or grazing state land, where the lease term begins after February 28 in the initial year of the lease, shall be for the whole of the yearly rate for the fractional part of the initial year if the lease term begins prior to July 1 in such fractional part of year, and for one-half the yearly rate for such fractional part of the year if the lease term begins after June 30 in the initial year and prior to the succeeding February 28.