Abstract: A granular herbicide or other agricultural chemical is applied using an applicator including a hopper with orifices in its base for discharging the granular material onto metering wheels mounted on a drive shaft beneath the hopper, the wheels feeding the material to a spreader; a motor for driving the shaft to rotate the wheels; and a control circuit which monitors the speed of the motor by constantly monitoring an A.C. feedback from such motor, and controls motor speed by adjusting the current fed to the motor to compensate for speed changes of the motor.