Evaluation of Evapotranspiration-Based and Soil-Moisture-Based Irrigation Control in Turf

Abstract

A study was initiated in Fall 2006 in Raleigh, North Carolina to compare two types of commercially available irrigation control technologies, one based on estimates of evapotranspiration (ET) and the other based on feedback from soil moisture sensors. Water applied and turf quality from one ET-based system and two sensor-based systems were compared to a system using a standard time-based irrigation schedule. The effect of irrigation frequency was also a part of the study. Estimates of turf ET were obtained from the Penman-Monteith equation using on-site weather data, and also from an atmometer. Results from the twenty week evaluation in 2007 showed that on average the "add-on" soil-moisture-based system evaluated applied the least amount of water while the ETbased system evaluated applied the most water. Weekly irrigation frequencies used the least amount of water, followed by biweekly and daily frequencies in increasing amounts when averaged across all technologies. Minimally acceptable turf quality was maintained by all technologies and frequencies through most of the study, but turf quality declined substantially the last month of the study for the add-on system and standard timer-based system. The "on-demand" sensor-based system resulted in the best combination of water efficiency and turf quality.

Reducing turfgrass water consumption using sensor nodes and an adaptive irrigation controller

“…Previous work has shown that water use efficiency can be improved through the addition of add-on sensors to existing irrigation controllers or through the use of more sophisticated controllers [3], [4], [8], [9], [10]. The types of control systems that are used in common practice can be classified as rainfall shutoff sensors (RS), soil moisture sensors (SMS) and evapotranspiration controllers (ET) [9].…”

“…If used in an area with a large variance in terms of local climate, the performance of the unit may lead to less than optimal results. Extensive testing in North Carolina has shown that ET systems produced no savings in water due to overestimation in terms of evapotranspiration demands [8].…”

Residential landscape water use in 13 North Carolina communities

“…In their 2008 field study in Charlotte, N.C., Grabow et al found that smart controllers applied more water on average than standard operating systems or systems regulated by soil moisture. Turf quality was lower for both the standard timer and soil moisture-based systems, whereas systems with smart controllers provided the highest-quality turf with the best water efficiency (Grabow et al, 2008). Additional research is needed to confirm the type of smart systems in use and to determine the true efficiency of each type of irrigation system.…”

Design and Implementation of Solar Powered Automatic Irrigation System

“…Time of operation (irrigation time -hrs per day) is calculated according to volume of water (water requirement -litres per day) required and the average flow rate of water (application rate -litres per hours). A timer starts and stops the irrigation process [8,9].…”