Smart Irrigation Controllers – Weather-Based Irrigation Control Introduction
Smart controllers are an emerging technology for adjusting irrigation applications based on actual weather and soil conditions. The concept of adjusting irrigation application to meet prevailing climate and weather conditions is as old as irrigated agriculture. The technology to control irrigation application automatically has been included in large-scale commercial systems for some time, but is relatively new to the residential and small commercial sectors. Over the past five years the number of smart controller products on the market has increased dramatically with different manufacturers opting for different control technology solutions.
According to the Irrigation Association’s Smart Controller Testing, “All 'smart' irrigation system controllers use either weather and/or site data as a basis for scheduling.”
Two fundamental irrigation control technologies have been implemented to manage water use in the current crop of smart controllers – (1) sensor based control; or (2) signal based control.
A sensor-based controller uses real-time measurements of one or more locally measured factors to adjust irrigation timing. The factors typically considered include: temperature, rainfall, humidity, solar radiation, and soil moisture. A sensor-based system often has historic weather information (i.e. an ET curve) for the site location programmed into memory and then uses the sensor information to modify the expected irrigation requirement for the day.
A study of soil moisture sensor-based irrigation controllers conducted at the University of Florida is available here:
Dukes, M. et al (2008) Evaluation of Soil Moisture-based on-demand Irrigation Controllers
A signal-based controller receives a regular signal of prevailing weather conditions via radio, telephone, cable, cellular, web, or pager technology. The signal typically comes from a local weather station (or series of weather stations) and usually updates the current evapotranspiration rate to the controller.