A system for use with a combine harvester (10) comprises a plurality of sensors (150) to detect the uniformity of crop material being conveyed from the threshing portion (14) of the combine to a cleaning system (80) including at least one sieve. A system is provided that utilizes this plurality of sensors (150) to provide substantially automatic control of combine parameters that mitigate the non-uniformity of a grain bed in the cleaning system (80). The system may also inform an operator of a suggested manual adjustment to mitigate the non-uniformity.
