A fertilizer system includes a supply vessel pressurized by anhydrous ammonia vapor. The fertilizer passes through a heat exchanger. Cooled fertilizer passes through a flow meter, an on/off valve and to a variable orifice distribution assembly body. A cage with axially elongated cage slots is press fit in a body bore with each slot aligned with an outlet port. Each port is connected to a soil knife by a conduit line. A piston with axially elongated piston slots is axially slidable in the cage. Each piston slot is moved axially in the cage to cooperate with a cage slot. An actuator moves the piston to a position that blocks flow through the piston slots and positions in which fertilizer flows through each piston slot and portions of each cage slot in communication with a piston slot. Vapor pressure in the supply vessel moves fertilizer to the knife opener.
