An assembly to distribute flowable particulate material, the assembly including: a conduit to which the material is delivered and to which an airstream is supplied to move the material along the conduit to a delivery downstream destination; material delivery means connected to the conduit for delivery of material to the downstream destination; control means operatively associated with the material delivery means to selectively deliver a pre-determined rate of the material to a separator to engage the airstream to concentrate the material in a portion of the airstream, the separator being positioned within the conduit upstream of the material delivery means; air distribution means in constant fluid communication with the separator and the material delivery means to control airflow to the material delivery means.