Abstract: An agricultural machine having drivable members for working the soil or crop or both. Either the agricultural machine or a tractor connected therewith has a storage medium which may be a computer memory in which a desired relationship between the rpm of the working member and the driving velocity of the agricultural machine is stored. The agricultural machine includes a governor or control mechanism for regulating, on the basis of the relationship stored in the storage medium, the rpm of the working member in dependence on the agricultural machine's velocity. In this manner, the optimum rpm for the driven working member can be set for any driving velocity of the machine to maximize the results obtained by the working member in improved soil or crop conditions or both.