Evaluation and Demonstration of Evapotranspiration-Based Irrigation Controllers

Irrigation systems need to become more efficient to minimize the use of limited water resources while maintaining landscapes of acceptable quality to consumers. This manuscript gives a preliminary report on the evaluation of three commercially available evapotranspiration (ET) based controllers in residential landscaped plots with respect to irrigation application and landscape quality compared to a homeowner irrigation schedule. The irrigation treatments were as follows: T1, Weathermatic Smart Line Series controller; T2, Toro Intelli-sense; T3, ETwater Smart Controller 100; T4, a time-based treatment; and T5, 60% of T4. This paper reports preliminary results from May 25, 2006 to November 30, 2006. T1 overestimated ETo by 32%, but applied less water than all other treatments during the summer season. Water savings occurred even though ETo was overestimated due to an underestimation of the crop coefficient for warm season turfgrass programmed into the controller (0.60) and due to frequent irrigation event bypass during the rainy summer season. The Weathermatic controller applied 11% and 14% less water than the theoretical gross irrigation requirement during the summer and fall seasons, respectively. The Toro Intelli-sense controller applied 126 mm in the fall, which was 40% less than theoretical requirements, and had the most accurate ETo of all the controllers. The ET water controller overestimated ETo by 7% and applied 63% more irrigation water than was required theoretically. During this preliminary testing, the ET controllers did not result in turf quality below acceptable levels.