A seed treatment system incorporates an incline conveyor to mix freshly treated seed. A metered seed flow is maintained. A treatment applicator positioned above a tail end of the incline conveyor applies a seed treatment to the metered seed flow to form a treated seed flow. The treated seed flow freefalls into a transition zone and pre-mixes before moving upward within the incline conveyor. An eddy may form within the treated seed flow due to a partial obstruction within the incline conveyor. A prescribed amount of the treated seed flow backflows into the eddy in a cascading manner. Backflow movement may be contrary to conveyance of a substantial amount of the treated seed up through the incline conveyor. The seed treatment distributes about the treated seed flow within the incline conveyor. The treated seed flow discharges with complete cleanout at a head end of the incline conveyor.