Preliminary Results for Bench Testing of Evapotranspiration-Based Irrigation Controllers in Florida

The Irrigation Association has developed a smart water application technologies (SWAT) testing protocol for ET controllers that describes a procedure for testing the efficacy of ET controllers. The test requirements include a minimum of thirty consecutive days with 63.5 mm of reference evapotranspiration (ET_o) and 10.2 mm of rainfall. The objectives of this study are to duplicate the soil water balance calculations specified by the SWAT test and recreate the SWAT bench test in a humid region using ET controllers previously tested under the SWAT protocol in an arid climate. Three brands of ET controllers previously tested under the SWAT protocol by CIT were installed at the Agricultural and Biological Engineering campus research facility (Gainesville, FL). The controllers are as follows: Weathermatic SL1600 with SLW20 weather monitor, Toro Intelli-sense duplicates utilizing the WeatherTRAK ET Everywhere Service, and ETwater Smart Controller 100 duplicates. Duplicate controllers were distinguished by whether they utilized an additional Mini-clik rain sensor denoted with a rain sensor (WRS) or without a rain sensor (WORS). The study period for each controller received less ET_o and rainfall compared to historical averages by 40% and 56%, respectively. The results found during the 2008 SWAT test showed that the ET controllers generally scored well in SWAT performance scores of scheduling efficiency and irrigation adequacy. However, the controllers resulted in lower scheduling efficiency scores than the original published results: 2.5% for the ETwater controllers, 14% by the Toro controllers, and 5.6% by the Weathermatic. It is likely that manufacturers would have opted to not publish these results as a SWAT score and restarted the test with minor adjustments. The SWAT test determines whether the controllers have accurate irrigation scheduling capabilities and does not rate the potential for a controller to conserve water. The SWAT testing protocol should be clearly outlined and detailed enough for results to be reproducible if it will continue to be used as an industry standard.