Abstract: Apparatus and method for automatically and continuously feeding, blending and mixing particulate material. In a non-mixing mode, a primary material is gravity fed through a vertical flow tube disposed in a chamber. Material flows into the chamber until an equilibrium level is established within the chamber. The volume of material fed through the system is governed by the through-put of a take-off screw, which communicates with a port in the bottom of the chamber. In a mixing mode, secondary materials, such as additives, are metered into the chamber at a point above the equilibrium mixing level, which secondary materials are mixed with the primary material, thereby automatically proportioning the final product feed. The vertical flow tube can be rotatable about its longitudinal axis in either mode to enhance mixing and feeding.