An image capture device captures an image of crop after it has been processed by a kernel processing unit on a forage harvester. A size distribution indicative of the distribution of kernel fragment sizes in the harvested crop is identified from the image captured by the image capture device. A control system generates control signals to control a speed differential in the speed of rotation of kernel processing rollers based on the size distribution. Control signals can also be generated to control a size of a gap between the kernel processing rollers.
