Starting in 1995, we initiated the use of automatic drip irrigation research based on soil moisture feedback. Soil moisture data to be used for feedback control of drip irrigation has been measured as soil water potential or soil water content. For soil water potential, granular matrix sensors (GMS; Watermark Soil Moisture Sensors, Irrometer Co., Riverside, Calif.) or tensiometers with pressure transducers are connected to a datalogger via multiplexers (Campbell Scientific, Logan, Utah). The datalogger is programmed to read the sensors in each zone several times a day and irrigate each zone as necessary according to pre-established criteria. Irrigations are controlled by the datalogger signaling a controller connected to solenoid valves. Using this system, irrigation criteria for onion and potato were determined for subsurface drip irrigation. This system was also used to demonstrate lower N fertilizer requirements for drip irrigated onion, evaluate irrigation intensity for drip irrigated onion, and the effect of short water stress on onion quality. Volumetric soil water content is measured by time domain reflectometry (TDR, Acclima, Meridian, ID). The Acclima controller reads the sensors and controls irrigations using solenoid valves. The volumetric soil water content criterion for initiating irrigations with the Acclima system was determined by comparison to soil water potential data. The criterion for the Acclima system had to be adjusted separately for each of three locations in the field. In 2004 two other dataloggers used to automate irrigations with the use of radio telemetry were tested with GMS: Automata, Inc. (Nevada City, CA) and Irrometer Monitor. Both systems use dataloggers in the field that transmit soil water potential data via radio to an office computer. The office computer collects and stores the data and makes irrigation decisions.