Iowa Code § 9G.2: Separate grants.

Separate tract books shall be kept for the university lands, the saline lands, the half-million acre grant, the sixteenth sections, the swamplands, and such other lands as the state now owns or may hereafter own, so that each description of state lands shall be kept separate from all others, and each set of tract books shall be a complete record of all the lands to which they relate.