An automated mechanical loading system for loading seedling carriers into a transporter bin for transport to the field for planting. The system of the present invention includes a transport bin having a plurality of rails mounted on the inside walls of the bin for accepting a plurality of carriers, power driven projections slidably mounted on sleds which are fixedly mounted to the top frame of a lift for urging one or more carriers into a preselected set of opposing rails in the bin. The lift controls the height of the sled so that the carriers are urged into the preselected set of rails in the bin. A mechanically referenced coupler is included for securing the lift to the bin to restrict movement of the lift relative to the bin into which the seedling carriers are to be loaded during the automated loading operation.