Abstract: Apparatus for treating the surface of bulbous or tuberous crops, comprising a substantially tubular treatment channel inclining upwards in the main direction of transport and comprising a top wall and a bottom wall, the bottom wall being made up of a number of drivable parallel rollers provided with treatment elements, and the top wall consisting of the lower part of a drivable endless conveyor. For the purpose of modifying the channel height, the top wall and the bottom wall are movable relative to each other longitudinally as well as perpendicularly. The lowermost rollers can form a receptacle reaching as far as before the foremost point of the conveyor belt.