Neb. Rev. Stat. §§ 46-1,112
Any irrigation district in this state having valid and unpaid bonds outstanding may by contract with the owners or holders thereof, or by other lawful means, provide for the extension of the time of payment thereof for any period not exceeding forty years, and may provide for the payment annually or semiannually of any rate of interest and for the payment of both principal and interest as one sum in any desired percentage per annum. Such district may also provide for the payment or refunding of such bonds by the issue and sale or the issue and exchange therefor of bonds maturing in any period not exceeding forty years, in an amount equal to the principal debt and the total interest to accrue thereon during the term of the bond at any agreed rate, and may make such bonds payable in installments equal to two percent of the principal and interest each year for the first four years; four percent of the principal and interest each year for the next two years; and six percent of the principal and interest each year for the next fourteen years; or if the bond term be more than twenty years, then in substantially proportionate installments.
Neb. Rev. Stat. §§ 46-1,112