Abstract: An anhydrous ammonia fertilizer injector includes a tool bar frame with multiple knife injectors. Vapor pressure of the fertilizer forces liquid from a tank through hoses and a vapor separator to a pump. The pump increases pressure above the vapor pressure. Liquid fertilizer passes from the pump through a flow rate sensor, a servo controller and to a manifold. Discharge fittings on the manifold hold orifices. Discharge hoses convey fertilizer from each discharge fitting to each knife. A pressure transducer in each fitting downstream from the orifice sends current pressure readings to a monitor console. The console identifies the largest number of transducer pressures that have readings within a set pressure difference from each reading. The average of the maximum and minimum pressures identified is the center of an acceptable pressure band. A selected deviation sets band limits. The console displays discharge hoses with pressures outside the band limits.