An agricultural implement has a product supply chamber, and a pair of transversely extending product delivering booms, each with a plurality of conduits of varying lengths terminating in product distributing nozzles. A fan supplies air to a mixing chamber which also receives product from the supply chamber providing an air entrained flow of product to each conduit. A controller monitors product delivery and controls implement operation. Each conduit has a pressure tap near the nozzle for providing the controller with a pressure differential indication. The controller initiates a corrective action modifying the operation of the delivery system when a predetermined pressure differential threshold is exceeded. The corrective action may include an increased air flow volume, an additional burst of higher pressure air into the conduit, a temporary increase in air flow from the air flow source, or a reduction in the rate of product flow from the supply chamber.