Evaluation of Irrigation Scheduling Efficiency and Adequacy by Various Control Technologies Compared to Theoretical Irrigation Requirement

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 comparing the adequacy and efficiency of the irrigation schedules for each control device with an irrigation schedule developed using a theoretical soil water balance. Testing was performed on a soil moisture sensor (SMS, LawnLogic) at a low and a medium soil moisture threshold setting. Mini-Clik rain sensors (RS) comprised four treatments, with one treatment pre-set for 3 mm of rainfall and an irrigation frequency of 7 d/wk. The other three RS treatments had sensors pre-set to bypass irrigation for 6 mm of rainfall and irrigation schedules of either 1 or 2 d/wk. An ET controller was also tested, the Toro Intelli-Sense controller (TORO). A time-based treatment with irrigation 2 d/wk and no rain sensor (WOS) was established as a comparison. In general the irrigation schedule for all treatments was more adequate during the fall months of testing than the spring months. Efficiency decreased for most treatments in the fall months of testing. Adequacy values calculated for 30-day running totals tended to vary greatly during a testing period. During the spring months of testing the average range in 30-day adequacy ratings was 24% and during the fall months the average range was 21%. The range in adequacy was as high as 63% during testing for one treatment. Looking at only one 30-day testing period may not fully capture the adequacy of an irrigation control device.