Fuente: Wipo "precision farming" A system for control of operational parameters within agricultural implements such as seed planters includes an agricultural work vehicle such as a tractor with an operator's station; an agricultural implement connected to the vehicle; a control subsystem including means for inputting a set point and for providing a control signal, located at the operator's station; a display connected to the control subsystem and located at the operator's station; an actuator connected to the control subsystem and located upon the implement; and a sensor connected to the display and located upon the implement. In one embodiment, the system further includes a source of low pressure air such as a fan, the implement is a seed planter having at least one substantially closed hopper or bin pressurized by the air, the actuator is a fan drive speed control apparatus, and the sensor is a pressure transducer configured to measure air pressure within the bin and connected to both the control subsystem and the display. The control subsystem causes the fan drive speed control apparatus to vary fan speed and, fan outlet pressure being a function of fan speed, thereby controllably modulate air pressure within the bin.