A sod harvester can include a preliminary stacking head for stacking slabs of sod prior to the stacked slabs being removed from a stacking conveyor for stacking on a pallet. In this way, the stacking head can remove multiple layers of sod during a single stacking operation. The preliminary stacking head can be positioned overtop a conveyor and can be configured to pick up a slab of sod as the slab travels along the conveyor. The preliminary stacking head can then drop the slab on top of a trailing slab thereby forming a stack of slabs on the conveyor. The conveyor over which the preliminary stacking head is positioned can be an inclined conveyor that transports slabs of sod from the ground to a stacking conveyor.