Abstract: A flow rate and droplet size control system for a spray system including a spray liquid source, a pump, a spray liquid line and a nozzle assembly. The control system includes a setpoint conversion subroutine for independently controlling the flow rate and volume median droplet size setpoints. The control system also includes performance envelopes for various nozzle tips. An independent flow rate and droplet size control method is provided for use with the control system. A position-responsive control system receives information pertaining to the boundaries of spray zones and spray conditions, such as application rates and volume median droplet diameters associated with the spray zones. The position-responsive control system monitors the position of a spray vehicle, which can comprise a ground vehicle or an aircraft. The position-based control system changes the spray system operating conditions in response to the sprayer vehicle position.