The board shall provide for the collection of taxes from the benefit district in such annual installments as it may determine, extending over not more than fifteen years, and may borrow money in advance of the collection of such taxes, in which event an amount sufficient to pay the annual interest shall be collected in addition to the principal. The taxes so assessed and levied shall be a lien upon the land and be collected at the same time and in the same manner that state and county taxes are collected. A separate assessment roll shall be provided by the board, and the assessor shall assess the lands in each benefit district separately, together with the benefit tax assessed thereon. He shall also mark in red ink on the general assessment roll the particular lands the benefits of which have been assessed.