Abstract: A rotary mixer utilizes position control technology to determine the position of the rotary mixer on a work surface and a controller determines whether an intended path across a work surface will overlap with a previously pulverized, mixed and modified surface. The rotary mixer utilizes at least one fluid spray bar in the rotor chamber or mixing chamber that extends along the width of the rotor. The fluid spray bar includes a plurality of nozzles spaced apart along the fluid spray bar that may he individually controlled by a nozzle actuator. In the event such an overlap is occurring or will occur, to avoid the application of excess fluid to the already modified surface, the controller directs the nozzle actuator to either reduce or shut off flow through the nozzles that are in alignment with the already modified surface.