The invention is directed broadly to an entrainment unit for distributing seed, comprising: a seed chamber for seed in bulk； a mixing chamber for mixing seed and air, the mixing chamber having an outlet for discharging entrained seeds； and an air supply unit for: (a) supplying a first air flow to the seed chamber and entraining and transporting seed to the mixing chamber, and (b) supplying a second air flow to the mixing chamber for forming a combined air flow that entrains the seed and transports the seed through the discharge outlet.
