An agricultural machine (100, 180) applies liquid material to a field. Valve control signals control valves (109, 204) to apply the liquid material. Row pressure on the agricultural machine is sensed (127, 210) to identify when the valve is opened to apply the liquid material. A flow meter (131, 206) senses a flow of liquid applied to the field. The valve control signals are generated, based on the row pressure, and the sensed flow.