Evaluation of Evapotranspiration and Soil Moisture-Based Irrigation Control on Turfgrass

A variety of commercially available technologies for reducing residential irrigation water use are available to homeowners. These technologies include soil moisture sensors, rain sensors and evapotranspiration (ET) based controllers. The purpose of this research was to evaluate the effectiveness of these various technologies based on irrigation applied and turf grass quality measurements. Testing was performed on two types of soil moisture sensors (SMS, LawnLogic® and the Acclima Digital TDT® RS500) at low, medium, and high soil moisture threshold settings. Mini-Clik® rain sensors comprised seven time-based treatments, with three treatments pre-set for 3 mm of rainfall and the remaining 4 rain sensor treatments had sensors pre-set to bypass irrigation for 6 mm of rainfall. Two ET controllers were also tested, the Toro Intelli-Sense controller and the Rain Bird® ET Manager^TM. A time-based treatment with two days of irrigation per week and no rain sensor (2-WORS) was established as a comparison. SMS-based treatments resulted in 0–63% reductions in water use compared to 2-WORS. Rain sensor treatments resulted in 7–33% reductions in water use. ET-based irrigation resulted in 36% to 59% reductions in water use compared to 2-WORS. The SMS treatments at the low threshold settings resulted in high water savings, but reduced turf quality to unacceptable levels. The medium threshold setting SMS-based, time-based and both of the ET-based treatments produced good turf grass quality while reducing irrigation water use compared to 2-WORS. Savings for the medium SMS-based systems ranged from 11–28%.