VARIABLE-RATE, DIGITALLY CONTROLLED METERING DEVICE

During the past decade, there has been increasing interest in applying water and chemicals to crops based on need or yield potential rather than applying uniformly to the entire field. While ground-driven variable-rate chemical application equipment is now being used, most irrigation systems continue to apply nominally uniform water depths. Our objective was to make variable-rate irrigation applications possible by developing a digitally controlled metering device. The device consists of a reservoir that is alternately filled and emptied at a rate determined by a digital pulse from an external source and requires pressurized sources of water and air. The flow rate can be altered by changing the cycle duration and frequency, by changing air and water pressure, or by exchanging the reservoir with one of different volume. Tests with prototypes indicate reproducible flow rates for a range of operating pressures and discharge cycle durations. Various sprinklers or nozzles may be attached to the outlet if specific distribution patterns are desired. Additionally, the metering device can be used in a wide variety of applications with a variety of fluids or gases for variable-rate flow or injection of a fluid into either another fluid or gas.