An air distribution apparatus including a manifold body and a plurality of ports defined through a wall of the manifold body. The apparatus also includes a delivery conduit connected to each one of the 5 plurality of ports. On at least one of the plurality of ports, a port valve configured to communicate an interior of the manifold body with the delivery conduit associated with the at least one of the plurality of ports. The apparatus also includes a supply conduit connected at an output end thereof to the interior of the manifold body and connected at an input end thereof to receive a product air stream with agricultural products entrained therein. The apparatus also includes an exhaust orifice 10 defined in the supply conduit and an exhaust valve configured to control a flow of pressurized air from an interior of the supply conduit through the exhaust orifice. The port valve and exhaust valve are controlled to operate oppositely to each other between open and closed positions of each valve such that when th
