In the silo unloader art, wherein a bottom unloader is used, and specifically an unloader of the generally central discharge type, wherein an auger delivers silage to the central zone of a silo, as the auger rotates on its own axis, and sweeps across the bottom of a silo, to a passageway through the floor of the silo, generally at the center of the silo, an openable closure is provided for the silo, for controlling the flow of silage through the passageways. Particularly, when the silo is closed down for the night, and when the silage is of the dry, granular, readily flowable type, the openable closure allows the passageways to be closed so as not to allow silage to build up and become compacted in the passageway area beneath the silo floor and around the silo exit auger.