A method and apparatus for controlling and monitoring the application rate of the anhydrous ammonia to the soil. A heat exchanger is used to maintain the anhydrous ammonia in a liquid state so that a flow control valve coupled to the heat exchanger can accurately control the rate of flow of liquid anhydrous ammonia to a manifold. Separate lines connected to the manifold distribute the liquid anhydrous ammonia to nozzles associated with earthworking tools to incorporate the ammonia into the soil. A portion of the ammonia from the manifold is directed back to an expansion chamber in the heat exchanger. The ammonia in the expansion chamber partially changes from a liquid to a vapor, thereby lowering the temperature of the ammonia in the expansion chamber and transferring heat from the liquid anhydrous ammonia in the heat exchanger to thereby maintain the ammonia in the liquid state. Lines carry the ammonia from the expansion chamber to nozzles associated with earthworking tools to incorporate the ammonia into the soil.