A root crop harvester comprises means for picking up a mixture of roots, dirt and debris from the surface of a cultivated field and conveying the mixture upwardly and rearwardly along the harvester. The mixture is cleaned of small articles of dirt and debris by apertures along the conveyor means, ribbed rollers and the like. The partially cleaned mixture is passed to sorting conveyors which counterrotate to convey approximately one-half (1/2) of the mixture towards each side of the harvester. Sources of light are positioned to transmit light along the terminal ends of the sorting conveyors and a plurality of light sensors are positioned to receive light reflected from objects located at the terminal ends of the sorting conveyors. The reflected light is processed to generate root signals and dirt/debris signals. Rejecting fingers respond to the root signals to pass roots to a root crop conveyor and respond to dirt/debris signals to pass dirt and debris to a dirt and debris conveyor. The disclosed apparatus and method allow for mass flow sorting as well as either active or passive dirt and debris rejection.