The device according to the invention comprises a bar that includes several consecutive ducts with at least one inlet connected to a source of the liquid product and outlets communicating with nozzles. The device further comprises several sensors for measuring a physical property making it possible to determine a pressure difference between ducts or a pressure in one respective duct, several members designed to vary the pressures inside respective ducts, as well as at least one control unit estimating the pressure differences between ducts and driving the members to reduce those pressure differences or equalize those pressures. This device thus limits the pressure differences, and therefore flow differences, of the liquid product between the nozzles, in particular between the ends of very long bars moving over significant bankings.
