The seed distribution tower of an air seeder splits a single, primary stream of conveying air and seeds into a plurality of secondary streams for delivery to openers that deposit the seeds into the ground as the seeder advances. As seeds enter the head of the tower in an upward vertical direction through an inlet at the bottom of the head, they are scattered 360° in a horizontal direction by an inverted, overhead distribution cone. The inlet through which the seeds enter the distribution head has an eased configuration to reduce turbulence and promote laminar flow within the head during the dramatic transition from vertical to horizontal movement. Sensitive components such as tram line valves, solenoid actuators, and blockage sensors are protectively housed within the interior of the distribution head to avoid exposure to hostile environmental elements. The outlets through which the secondary streams exit the head are constructed as modules that can be individually installed and replaced without disassembling the entire head. Shut-off valves and/or flow sensors may or may not be incorporated into certain or all of the modules to provide optimum user flexibility.
